Combined simulation of combustion and gas flow in a grate-type incinerator

Computational fluid dynamic (CFD) analysis of the thermal flow in the combustion chamber of a solid waste incinerator provides crucial insight into the incinerator's performance. However, the interrelation of the gas flow with the burning waste has not been adequately treated in many CFD models. A strategy for a combined simulation of the waste combustion and the gas flow in the furnace is introduced here. When coupled with CFD, a model of the waste combustion in the bed provides the inlet conditions for the gas flow field and receives the radiative heat flux onto the bed from the furnace wall and gaseous species. An unsteady one-dimensional bed model was used for the test simulation, in which the moving bed was treated as a packed bed of homogeneous fuel particles. The simulation results show the physical processes of the waste combustion and its interaction with the gas flow for various operational parameters.     

Photosynthetic characteristics of marine Synechococcus spp. with special reference to light environments near the bottom of the euphotic zone of the open ocean

The present study aimed to resolve the question why marine Synechococcus spp. abundantly occur even at the bottom of the euphotic zone in the Kuroshio are. Photosynthesis under such conditions was examined using simulated blue-green model light (BGL). Results indicated that photosynthesis of marine Synechococcus spp. under BGL is as active enough to support growth of these organisms. Examination of light-harvesting under BGL indicated that active photosynthesis is permitted by an unusually high abundance of phycoerythrin (PE), which is the main light-harvesting pigment for photosystem II (PSII), due to a phycobilisome (PBS) structure which is different from ordinary hemidiscoidals. Although the absorption maximum of PE is located at longer wavelengths than the energy maximum of BGL, PE was found to absorb BGL significantly. Thus, BGL cannot be a typical photosystem I (PSI) light. PSII is also significantly excited by BGL. Carotenoids, which largely absorb BGL, were found to be effective in light-harvesting for PSI. Based on the results obtained, possible reasons why marine Synechococcus spp. commonly occur in warm waters were discussed. Two strains of Synechococcus spp. isolated from the Gulf Stream in 1981 and from Kuroshio, Japan in 1983 were used in the present study.     

Minimum effective release rate of antifoulants.1. Effects of zosteric acid at Ford Island,Hawaii (USA)

Minimum effective release rate (MERR) of zosteric acid (ZA) was studied at Ford Island. At laboratory condition, spore attachment in Enteromorpha intestinalis was inhibited significantly at 28.2 microg cm2 of ZA. More than 95% reduction in spore attachment was achieved in Ulva fasciata at 2,000 microM of ZA through membrane diffusion system. At 40 cm depth level larval settlement was high with maximum number of Hydroides elegans settlement. The overall larval settlement was increased with increasing days of exposure. The MERR of 10 microg cm(-2) d(-1) ZA inhibited 50% of the larval settlement. However, the inhibition rate was not proportionate to the antifouling ZA concentration. Using MERR membrane diffusion system an effective antifouling strategy was suggested for Ford Island.     

Experimental and numerical calculations of waste R-134a thermal decomposition for energy and fluorine material recovery

Considering the global warming potential of R-134a (C₂H₂F₄) with the substantial generation of this refrigerant as waste material in various industrial sectors, the development of proper thermal destruction method of R-134a is of great practical significance. For this, experiment and numerical calculations have initially made for a tubular-type furnace in order to figure out the basic combustion characteristics of R-134a. A series of experimental investigations for the thermal decomposition of R-134a have been made as a function of wall temperature of tubular furnace and important reacting species such as O₂ and H₂O necessary for the decomposition of C₂H₂F₄ into HF, CO₂ and H₂O. In general, the thermal decomposition of R-134a is successfully made for the condition of temperature above 800 °C with the supply of stoichiometric amount of O₂ and these results are well agreed with numerical prediction. And this information is employed for the simulation of a full-scale, practical incinerator used for the CDM project. For this, numerical investigation has been made for a commercial-scale incinerator using CH₄–air flames for the proper destruction C₂H₂F₄ together with the control of pollutants such as CO and NO. In general, the destruction rate of C₂H₂F₄ appears more than 99.99 % and the generation of CO and NO species appears rather sensitive to the operational condition such as amount of water vapor. The numerical method of HFCs (hydrofluorocarbons) thermal treatment shows high possibility as a viable tool for the proper design and optimal determination of the operational condition for a HFCs incinerator.     

The Mini-Cup Jelly Court Cases: A Comparative Analysis from a Food Ethics Perspective

This study compares and analyzes separate court rulings in three countries on “mini-cup jelly” (a firm jelly containing konjac and packaged in bite-sized plastic cups) from a food ethics perspective. While the Korean and US courts decided that the mini-cup jelly was defective, and that the manufacturers or importers were liable for damages in these cases, the Japanese court took an opposing stance in favor of the manufacturer. However, from an absolute and fundamental viewpoint, the jelly was unacceptable, ethically as well as legally, because it was unsafe, unwholesome, and unfit for children’s consumption. I argue that the ignoring or sidelining of fundamental principles of food ethics, especially “respect for life,” was at the core of these cases. If the manufacturers and importers had considered and prioritized the principles of food ethics over and above big sales and profits, the choking accidents could have been prevented. To conclude, it is very important to minimize risks by applying the principles of food ethics at the outset before any accidents can occur.     

Accumulation of paralytic shellfish poisoning toxins in planktonic copepods during a bloom of the toxic dinoflagellate<Emphasis Type="Italic"> Alexandrium tamarense</Emphasis> in Hiroshima Bay,western Japan

Concentrations of paralytic shellfish poisoning (PSP) toxins in toxic dinoflagellate cells and in marine planktonic copepods were monitored during the bloom of Alexandrium tamarense in Hiroshima Bay, western Japan. Concentration of the toxins retained by copepods was a function of the ambient toxin concentration, i.e. the product of A. tamarense cell density and cellular toxicity. The toxin concentration in copepods increased with the increase of toxicants in the seawater then leveled off, but decreased significantly at higher concentrations. In the field, the maximum toxin concentration was 1.2 pmol ind^-1, whereas in the laboratory, the copepod Acartia omorii accumulated a much higher concentration of PSP toxins (24 pmol ind^-1). Feeding avoidance against Alexandrium tamarense and a shift to alternative food sources such as diatoms in the field might keep their toxin levels lower than their potentially maximum level. The copepod toxin levels in the field were not so high as to cause an instantaneous lethal effect on their predator fishes but may reach possibly lethal levels after a few days' continuous feeding. Overall toxin retention by copepods after 12 h feeding and 2 h starvation was only 2.5% of total ingested toxins, which suggested that a significant amount of toxins was released into the seawater. Measurements of toxin reduction and gut evacuation suggested that the toxins were removed through both fecal evacuation and metabolism (e.g. excretion, decomposition and transformation). The results, as a whole, imply that copepods can be a link for PSP toxin flux in both pelagic and benthic food webs and can also be a sink for toxins by metabolizing and removing them from the environment.Communicated by T. Ikeda, Hakodate     

Optical and microphysical properties of severe haze and smoke aerosol measured by integrated remote sensing techniques in Gwangju,Korea

Aerosol optical and microphysical parameters from severe haze events observed in October 2005 at Gwangju, Korea (35.10°N, 126.53°E) were determined from the ground using a multi-wavelength Raman lidar, a sunphotometer, and a real-time carbon particle analyzer and from space using satellite retrievals. Two different aerosol types were identified based on the variability of optical characteristics for different air mass conditions. Retrievals of microphysical properties of the haze from the Raman lidar indicated distinct light-absorbing characteristics for different haze aerosols originating from eastern and northern China (haze) and eastern Siberia (forest-fire smoke). The haze transported from the west showed moderately higher absorbing characteristics (SSA = 0.90 ± 0.03, 532 nm) than from the northern direction (SSA = 0.96 ± 0.02). The organic/elemental carbon (OC/EC) ratio varied between 2.5 ± 0.4 and 4.1 ± 0.7.     

Degradation characteristics of toluene,benzene, ethylbenzene,and xylene by Stenotrophomonas maltophilia T3-c

Stenotrophomonas maltophilia T3-c, isolated from a biofilter for the removal of benzene, toluene, ethylbenzene, and xylene (BTEX), could grow in a mineral salt medium containing toluene, benzene, or ethylbenzene as the sole source of carbon. The effect of environmental factors such as initial toluene mass, medium pH, and temperature on the degradation rate of toluene was investigated. The cosubstrate interactions in the BTEX mixture by the isolate were also studied. Within the range of initial toluene mass (from 23 to 70 pmol), an increased substrate concentration increased the specific degradation of toluene by S. maltophilia T3-c. The toluene degradation activity of S. maltophilia T3-c could be maintained at a broad pH range from 5 to 8. The rates at 20 and 40 degrees C were 43 and 83%, respectively, of the rate at 30 degrees C. The specific degradation rates of toluene, benzene, and ethylbenzene by strain T3-c were 2.38, 4.25, and 2.06 micromol/g-DCW/hr. While xylene could not be utilized as a growth substrate by S. maltophilia T3-c, the presence of toluene resulted in the cometabolic degradation of xylene. The specific degradation rate of toluene was increased by the presence of benzene, ethylbenzene, or xylene in binary mixtures. The presence of toluene or xylene in binary mixtures with benzene increased the specific degradation rate of benzene. The presence of ethylbenzene in binary mixtures with benzene inhibited benzene degradation. The presence of more than three kinds of substrates inhibited the specific degradation rate of benzene. All BTEX mixtures, except tri-mixtures of benzene, ethylbenzene, and xylene or mixtures of all four substrates, had little effect on the degradation of ethylbenzene by S. maltophilia T3-c. The utilization preference of the substrates by S. maltophilia T3-c was as follows: ethylbenzene was degraded fastest, followed by toluene and benzene. However, the specific degradation rates of substrates, in order, were benzene, toluene, and ethylbenzene.     

Ball end milling mechanistic model based on a voxel-based geometric representation and a ray casting technique

Prediction of machining forces involved in complex geometry can be valuable information for machine shops. This paper presents a mechanistic cutting force simulation model for ball end milling processes, using ray casting and voxel representation methods used in 3D computer graphics field. Using this method, instantaneous uncut chip cross sectional areas can be extracted, which can be used in cutting pressure coefficient extraction and machining simulation including machining forces and geometry of the workpiece. The major advantage of the proposed scheme is that it can simulate milling processes with arbitrary cutting tool geometry on a workpiece with complex geometry, using an algorithm with constant time complexity. A series of cutting experiments were carried out to validate the model.