Grouping strategies for MPS soot transport model and its application in large-scale enclosure fires

A soot transport model called Multi-Particle-Size model (MPS model) was developed to improve the prediction of soot movement by considering the uneven mass size distribution of soot particles and the influence of particle size on the gravitational settling. The model requires a sophisticated grouping strategy to divide the soot particles into several groups and determine the representative size for each group. In this paper, several soot particle grouping strategies and the method to calculate the representative sizes are developed with the aim of balancing the computational efficiency and the prediction accuracy of the model. The performance of the MPS model when different grouping strategies are applied is investigated through the comparison of the predicted movement of soot particles generated from several materials. Based on this analysis a grouping strategy that results in the identification of three groups is shown to be sufficient to represent the influence of particle size on the gravitational settling for a variety of combustible materials and the computational cost of the extra governing equations for the transport of soot particles in the groups is acceptable. Furthermore, the efficiency of the model is demonstrated by simulating soot movement in a large-scale industrial building with a high ceiling

Dietary calcium requirements of bighead carp (Aristichthys nobilis)

To investigate dietary calcium requirement of bighead carp (Aristichthys nobilis), six purified diets were formulated to contain different concentrations of calcium (0.09% (control), 0.43%, 0.76%, 1.12%, 1.44%, and 1.79% of dry diets). Each diet was hand-fed to triplicate 30 fish with an average initial body weight (3.31 ± 0.09 g) for 60 days. The results showed that weight gain (WG) and specific growth rate (SGR) significantly increased when dietary calcium level was from 0.09% to 0.76% (P < 0.05). The phosphorus and calcium contents of whole fish body were highest in the 0.76% and 1.12% group, respectively (P < 0.05). The serum phosphorus content in the 1.79% group was significantly lower than those in other groups (P < 0.05). As dietary calcium content was from 0.09% to 0.76%, the activities of lipase and proteinase in the intestine had a significant increase (P < 0.05), while the glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) activities were significantly decreased (P < 0.05). Based on quadratic curve model analysis with WG and WGR as the appraising criteria, the appropriate dietary requirement of calcium for the bighead carp larvae (3.31 ± 0.09 g) was 1.01% - 1.02%

A two-step method for predicting time to flashover in room corner test fires using cone calorimeter data

A method to predict time to flashover in ISO 9705 room corner fire tests based on cone calorimeter data is proposed in this paper. The method involves classification of materials and estimation of time to flashover as two steps in sequence. In the first step, the investigated material is classified into discriminating material groups. In the second step, the time to flashover is calculated with a derived formula for the corresponding material group, which contains material density, time to ignition and heat release rate collected from smallscale experiments. Compared with two existing models, the proposed method has improved the prediction precisions in both the time to flashover and classification of material categories for a wide range of materials

Simulating a rail car fire using flame spread model

In this paper, an enhanced flame spread model implemented in the SMARTFIRE CFD fire simulation software is used to simulate a rail car fire. The study focuses on three areas: demonstrating the shortcomings of the single criterion of surface ignition temperature in flame spread models; reproducing the rail car fire using the enhanced flame spread model and investigating the effects of configuration and burnable properties of interior materials on the fire development. The results show that the enhanced flame spread model is better able to reproduce the fire experiment results compared with flame spread models using the ignition temperature as the sole ignition criterion. The results also demonstrate that the configuration of the interior furniture and burnable properties of materials are important factors affecting the time to flashover

Simulating smoke transport in large scale enclosure fires using a multi-particle-size model

In Computational Fluid Dynamics (CFD) based fire simulation, the particle laden smoke is usually assumed to be in a gaseous state. This is due to the assumption that most of the smoke particles have diameters less than about 2.0 µm and so their settling velocities can be ignored compared with the intensive turbulent fire gas flow. This simplification can lead to severely under-predicted smoke levels in the lower layer at remote locations from the fire source. This problem is addressed in this paper through the development of a Multi-Particle-Size model which takes into consideration the uneven mass size distributions of smoke particles. The model divides the smoke particles into three groups with various diameter ranges. The transport of smoke particles in each group is represented by a governing equation, in which the gravitational force is addressed by adding a correction into the convection term. The efficiency of the model to reproduce smoke transport is demonstrated by simulating a large scale PVC-cable fire experiment conducted in a long corridor. Compared with a conventional smoke transport model, the new model is shown to be better able of reproducing the measured experimental smoke data and the recorded visibilities

Therapeutic Suppression of miR-4261 Attenuates Colorectal Cancer by Targeting MCC

The mutated in colorectal cancer (MCC) gene is an important colorectal tumor suppressor gene, although few studies have reported the microRNA(s) that could directly target MCC in colorectal cancer. Here, we used microRNA (miRNA) target prediction algorithms, and previously reported microarray data in human colorectal cancer found that only miR-4261 was predicted by all three databases to directly target MCC. Based on specimens from our own cohort of colorectal cancer patients, we further demonstrated that miR-4261 was overexpressed in colorectal cancer. Interestingly, overexpression of miR-4261 could enhance cell proliferation and G1/S phase transition of cell cycle, and promote cell migration in HCT116 and HT29 cells, while inhibition of miR-4261 had opposite effects. Luciferase reporter assay and western blot analysis confirmed MCC as a direct target of miR-4261. MCC small interfering RNA (siRNA) could abolish the suppressive effects of miR-4261 inhibitor on cell proliferation and migration in HCT116 and HT29 cell lines. Finally, we showed that therapeutic intervention with lentivirus-based miR-4261 sponge injection could effectively reduce tumor growth and inhibit cell proliferation in colorectal cancer xenograft. Collectively, our study is the first one to unravel the functional role of miR-4261, and it provides strong evidence that inhibition of miR-4261 through targeting of MCC might exert a therapeutic effect for colorectal cancer. Keywords: colorectal cancer, miR-4261, MC