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0 ; B, 1 m smhm(S -A)+ 0 a (9) The rate of gas absorptmn mto the slurry IS then calculated by eqn (9) and either eqn (4) or (5) When the sohd concentration IS h@ or the mterfacml area m the absorber IS small, the second term m the denommator of eqn (9) becomes dommant over the first one and & approaches

This note is concerned with the multiplicity of solutions for the factor of safety that may be obtained on the basis of the method of slices. Discontinuities in the function for the factor of safety are discussed and the reasons for false convergence in any iterative solution process are explored, with particular reference to the well-known Bishop simplified method (circular slip surfaces) and Janbu simplified or generalized method (slip surfaces of arbitrary shape). The note emphasizes that both the solution method and the method of searching for the critical slip surface must be considered in assessing the potential for numerical difficulties and false convergence. Direct search methods for optimization (e.g., the simplex reflection method) appear to be superior to the grid search or repeated trial methods in this respect. To avoid false convergence, the initially assumed value of factor of safety F 0 should be greater than β 1 (=−tan α 1 tan [Formula: see text]) where α 1 and [Formula: see text] are respectively the base inclination and internal friction angle of the first slice near the toe of a slope, the slice with the largest negative reverse inclination. A value of F 0 = 1 + β 1 , is recommended on the basis of experience. If there is no slice with a negative slope for any of the slip surfaces generated in the automatic, search process, then any positive value of F 0 will lead to true convergence for F. It is necessary to emphasize that no slip surface needs to be rejected for computational reasons except for Sarma's methods and similarly no artificial changes need to be made to the value of [Formula: see text] except for Sarma's methods. Key words: slope stability, convergence, limit equilibrium, analysis, optimization, slip surfaces, geological discontinuity, simplex reflection technique.

Of all sciences, chemistry is a branch that emphasizes practice. On the basis of fully realizing its characteristics, multi channel cultivation of students' scientific learning, methodology and creation will set a role model for quality oriented chemistry education in teachers school.

Zhundong low-rank coal is very likely to be utilized extensively in oxy-fired boilers in the near future. Its PM10 (particulate matter with an aerodynamic diameter of ≤10 μm) emission behaviors during oxy-fuel combustion need to be carefully studied before its large-scale use. The present study examines the emission behaviors of inorganic ultrafine particles (PM0.5, with an aerodynamic diameter of ≤0.5 μm), as well as PM10 during the combustion of Zhundong coal in air and oxy-fuel conditions (O2/CO2) at three characterized O2 input fractions, i.e., 21, 27 and 32 vol.%. The combustion experiments were carried out in a high-temperature drop-tube furnace (HDTF) at a combustion temperature of 1500 °C. The results show that PM0.5 is composed of Na, S, Mg and Ca, with total fractions of ~90%, while PM0.5–10 (with an aerodynamic diameter between 0.5 and 10 μm) predominantly contains Ca (~50–65%). At three characterized oxygen fractions during oxy-fuel combustion (OXY21, 27 and 32), the promoted O2 fraction was found to increase the yields of both PM0.5 and PM0.5–10. A higher particle-burning temperature and a lower CO2 fraction promote the reactions of both organically bound elements and inorganic minerals, increasing the partitioning of Mg and Ca and causing an increased yield of PM0.5. The yield of PM0.5 from air is high and similar to that from OXY32 while the yield of PM0.5–10 from air is similar to that from OXY27. The high yield of PM0.5 from air is mainly generated by the highest yields of Ca in four conditions.

A novel seismic retrofit technique, known as the section reduction (SR) technique, was proposed for reinforced concrete (RC) frames to realize the strong column and weak beam hierarchy. The SR technique involves the removing a portion of concrete at the bottom zone of the beam near the joint, along with shear strengthening of the weakened area using fiber-reinforced polymer (FRP). Preliminary experimental studies on RC beams with locally reduced cross sections (i.e., a gap) have demonstrated that the inclusion of a gap can effectively weaken the negative bending capacity of a T-shaped RC beam. However, there was no finite element (FE) approach for predicting the behaviour of such RC beams. Therefore, this paper aims at establishing a reliable FE approach for T-shaped RC beams with a gap. A total of five gap sizes were examined, including three small gap sizes and two large gap sizes. The applied FRP-strengthening system consisted of the CFRP U-jackets below and on both sides of the gap. In the proposed FE approach, two concrete cracking models available in ABAQUS/Explicit, including the concrete damaged plasticity (CDP) model and the brittle cracking (BC) model, were examined. Moreover, two tensile damage models were considered. The FE results showed that the CDP model with a power law tensile damage model is suitable for specimens that failed in a flexural mode, while the BC model with secant modulus of concrete adopted is suitable for specimens failing in a shear mode. The FE results also verified that increasing the gap height reduces the negative bending capacity of the beam more effectively than increasing the gap length, and the application of the FRP-strengthening system can enhance the ductility of the weakened beam. The proposed FE approach can be used for the subsequent proposal of strength model and design method of such beams.

In coal conversion processes, such as combustion or high-temperature gasification, the extent of pyrolysis is an important parameter which is affected by temperature. Increasing amounts of coal converted directly to gaseous species would reduce the remaining material which must be converted by the relatively slow char-gas reactions. Studies on this aspect, particularly at pressure and high temperatures, are scarce. To help fill in the data gaps, the present work has therefore been focused on the examination of pyrolysis at high temperatures (800 to 1600/sup 0/C), pressures (1 to 15 atm) and in various reacting and nonreacting gases. Devolatization generally increases with temperature in a manner consistent with the proposed three-stage mechanism for the evolution of volatiles. Results here show a plateau at 1200 to 1400/sup 0/C and a maximum devolatilization above 1500/sup 0/C. Reactive gases can interact with the freshly formed volatiles and affect the secondary char-forming reactions which can cause changes in the apparent percent pyrolysis. This was evident from the effects of moisture content, particle size, pressure and gaseous environment on the extent of pyrolysis. Reactivity of char formed in-situ and immediately reacted was found to be higher than reactivity of chars formed separately and then brought intomore » the reactive environment. It is suggested that morphological rearrangements may be important in pyrolysis and subsequent char reactions.« less

Results are presented of a study undertaken to analyze and assess fluidized bed oil shale combustion, particularly from an environmental standpoint. Oil shales are classified and characterized and their properties are described. Attention is focused on mineralogical composition, porosity, specific gravity, specific heat, calorific value, thermal conductivity, trace metal content, and sulfur and nitrogen content. The mechanisms and kinetics of oil shale retorting and combustion are discussed. The clean combustion of oil shale is examined and fluidized bed oil shale combustion is explored. The simulation of oil shale combustion in a fluidized bed, 6 inches in diameter, is described. The advantages of combustion in a fluidized bed are listed, including: (1) fluidized beds can be effectively used to burn oil shale to produce heat or steam at a high combustion frequency and (2) gaseous pollutants can be removed during combustion inside the bed. Disadvantages are noted, including: (1) the spent shale from a 10-ton steam/hour boiler is estimated to be 78 tons per day at the fresh oil shale feed rate of 104 tons per day; and (2) the fluidized bed must be maintained at a relatively low temperature of 810C.

The state-of-the-art of the theory and control of NO/sub x/ emissions from combustors is reviewed including the mechanisms and kinetics of the formation of thermal and fuel NO/sub x/, its destruction by reactions with char and reducing gases, and NO/sub x/ emissions control technology and mathematical modeling of fluidized-bed combustors. Practical conclusions are drawn, some unsolved problems are described, and recommendations are made as to various topics which require further study.

Based on the results of international researches and design feature of CPR1000 containment,the fragility curve for CPR1000 containment is studied.The operation pressure to put Containment Filtration and Exhaust System(EUF) into service is proposed.With different operation pressures,the radiological con-sequences has been compared.The results show that the pressure threshold for EUF operation can increase to 0.71MPa(g) and the starting time of the EUF is delayed about 1day and the accumulated activity to the envi-ronment is also decreased definitely.