Search

With the widespread use of ammonia in the industrial fields, more and more accidents are caused by ammonia leakage and dispersion. To study the dispersion law of ammonia in a food factory, small scale wind tunnel experiments were designed. Different initial conditions such as release flow rate, wind speed, release height and the heights of concentration sensors were considered. Ammonia concentration was measured near release source, obstacles and far from release source, respectively. The law of ammonia dispersion is determined by its physical properties, release source conditions and atmospheric environment. Ammonia concentrated in the axial direction and showed an upward movement near the source as ammonia's density is lower than the air. We obtained the law of ammonia dispersion in a food factory through experiments indicating that the concentration of each measuring point is proportional to the flow rate. With the increase of wind speed, the concentration of ammonia at different points first increased and then decreased. The results showed that the effect of ammonia dispersion was more obvious under the influence of the wind field. The maximum concentration can be reached under the wind speed range of 0.8–1.2 m/s. Changing the height of source and measuring point will make a great difference in the concentration of the measuring point. In the simulation work, RNG k-e model represents better agreement with the experimental data. Ammonia movement has a strong concentration gradient and the horizontal wind field streamlined ammonia movement.

To investigate the deformation and failure mechanism of the roadway under high in situ stresses at the 958 section in 2# mine in Jin Chuan, China, field and numerical investigations were conducted. Field investigations on the loosen ring of the roadway show that great roadway deformations and failure in surrounding rocks may result from poorly functioned bolts. Based on the old supporting system, a new supporting system characterized by the installation of steel pipe beams and the elongated bolts was proposed and applied in field. Field data indicate that the roof sag, rib convergence and floor heave significantly decrease. The numerical study illustrates that the properly functioned bolts and steel pipe beams are responsible for the decrease of roadway deformation. To further control the roadway deformation, two additional supporting systems were proposed and simulated. The increase of the bolt density contributes to reinforcement of the surrounding rocks and the floor heave in the first support system is under controlled. In the second support system, the installation of bolt on floor successfully restrains floor heaves accordingly.

With the widespread use of ammonia in the process industry, more and more accidents were caused by ammonia leakage and dispersion. The dispersion of ammonia is determined by its physical properties, release source conditions and atmospheric environment. Full-scale numerical simulation based on CFD theory was carried out to study the dispersion law of ammonia in a food factory. It was found that ammonia concentrated on the symmetric plane and showed an upward movement near the source. Moreover, the effect of pressure on the dispersion of ammonia was explored showing that the concentration of ammonia near the source increased with the increase of pressure, while the dispersion of ammonia far from the source is mainly influenced by wind field. Last but not the least, the dangerous area completely covers the obstacle region according to the harmful concentration, but the lethal concentration range and explosion range both only existed near the release source. Correspondingly, the concentration of ammonia in the region far from the symmetric plane can be regarded as a safe area. When the accident happens, one should stay away from the release source and evacuate towards the sides in a timely manner. We hope that this work can provide an effective method in predicting the impact of ammonia dispersion and can arouse concerns over the public safety.

A pH-responsive cellulose-g-P4VP copolymer was synthesized by atom transfer radical polymerization (ATRP) in ionic liquid 1-allyl-3-methylimidazolium chloride [AMIM]Cl. The polymer structure was characterized by Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The P4VP brushes that were covalently bonded to the cellulose backbone had a narrow molecular weight distribution, which was helpful for use in drug loading. The loading and controlled release of drug using aspirin as model drug in the micelles obtained the cellulose-g-P4VP copolymer was investigated. The structure and size of the copolymeric micelles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and ultraviolet–visible (UV-Vis) spectroscopy, respectively. Blank micelles presented a stably spherical morphology with dimeter about 90 nm in aqueous solution. The resultant micelles had clear pH-sensitivity with a pH-dependent phase transition point at a pH of about 5.7. Drug-loaded micelles had a spherical, core–shell structure with dimeter about 150 nm. The polymeric micelles revealed an excellent controlled drug release at different pH values and the cumulative release of aspirin in phosphate buffer reached to 86.4% at pH 5.8, 60.9% at pH 7.4 and 42.2% at pH 8.0.at 50 h. The pH-sensitive cellulose-g-P4VP copolymer had an enormous potential as carriers for released drug delivery.

Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens’, which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.

Water curtain system has been proved an effective mitigation measurement for ammonia spill dispersion. Calculating of ammonia cloud concentration with water curtain was less studied. This paper presents a steady-state calculation model to calculate open and forced ammonia spill dispersion. The formula of ammonia absorption was built and integrated into the calculation model. The calculated downwind ammonia concentrations for open and forced spill dispersion were reproduced and compared with literature using a statistical method. In addition, the relationship between ammonia concentration in water droplet and the droplet diameter was studied. The results display that the formula of ammonia absorption is suitable for calculating mass transfer process between the ammonia cloud and the water curtain. The calculation model presents good performances for open and forced ammonia spill dispersion. This study indicates that the calculation model can be satisfactory in determining the impact of open and forced ammonia spill dispersion and the design of water curtain mitigation system.

The technological conditions of absorption of H2S using pyrolusite ferric sulfate were studied. In this process, low cost raw materials are used, oxidation absorption of H2S and regeneration of ferric salt were realized simultaneously, and continuous operation can be achieved. Consequently, appropriate operating conditions were established: Room temperature; Concentration of sulfuric acid is 0.5 mol/L; Ferric concentration is 1.0 mol/L; Concentration of MnO2 is 3.0g /50mL. Under these conditions, the maximal ratio of absorption of 99.2% can be achieved in discontinuous operation process, and approximately 100% absorption of H2S can be achieved by multi-absorption in series and addition of pyrolusite and sulfuric acid in continuous operation process.

The molecular structure of the title molecule, C12H8BrN3Se, is built up from fused selenazolo and pyridine rings, linked to a 2-bromoaniline group. In the crystal, pairs of molecules are linked by N—H...N hydrogen bonds into dimers, forming eight-membered ring motifs.

By using a detailed configuration accounting method in the collisional radiative equilibrium model, and Cowans relativistic atomic structure code with respect to ionic averaged configurations and Hartree-Fock-Slater potential, we solve the rate equations for populations of all ionic and level populations of all excited states, in which main consider main atomic dynamic processes in a non-local thermodynamic equilibrium plasma can be considered, thereby obtaining the ionic populations and energy level populations and the ionic charge stage distribution and the average charge for Au. We also simulate and calculate the X-ray emission spectra of Au 5f—3d transition arrays. The calculated results are in good agreement with the experimental data for a well-characterized highly ionized Au plasma.

Based on the three-body model proposed by Ren and Xu[1]，an improvement on their variational wave function has been made. The structures and the interparticle correlations have been explored by inspecting the correlated densities. A direct veri-fication supporting the neutron halo structure has been found.