Search

Most solid rockets are powered by ammonium perchlorate (AP) composite propellant including aluminum particles. As aluminized composite propellant burns, aluminum particles agglomerate as large as above 100 μm diameter on the burning surface, which in turn affects propellant combustion characteristics. The development of composite propellants has a long history. Many studies of aluminum particle combustion have been conducted. Optical observations indicate that aluminum particles form agglomerates on the burning surface of aluminized composite propellant. They ignite on leaving the burning surface. Because the temperature gradient in the reaction zone near a burning surface influences the burning rate of a composite propellant, details of aluminum particle agglomeration, agglomerate ignition, and their effects on the temperature gradient must be investigated. In our previous studies, we measured the aluminum particle agglomerate diameter by optical observation and collecting particles. We observed particles on the burning surface, the reaction zone, and the luminous flame zone of an ammonium perchlorate (AP)/ammonium nitrate (AN) composite propellant. We confirmed that agglomeration occurred in the reaction zone and that the agglomerate diameter decreased with increasing the burning rate. In this study, observing aluminum particles in the reaction zone near the burning surface, we investigated the relation between the agglomerates and the burning rate. A decreased burning rate and increased added amount of aluminum particles caused a larger agglomerate diameter. Defining the extent of the distributed aluminum particles before they agglomerate as an agglomerate range, we found that the agglomerate range was constant irrespective of the added amount of aluminum particles. Furthermore, the agglomerate diameter was ascertained from the density of the added amount of aluminum particles in the agglomerate range. We concluded from the heat balance around the burning surface that the product of the agglomerate range and the burning rate was nearly constant irrespective of the added amount of aluminum particles. Moreover, the reduced burning rate increased the agglomerate range. [ABSTRACT FROM AUTHOR]

On the basis of the proposed algorithm for calculation of the hadron reaction rates, the space-time structure of the relativistic nucleus-nucleus collisions is studied. The reaction zones and the reaction frequencies for various types of reactions are calculated for Alternating Gradient Synchrotron (AGS) and Super Proton Synchrotron (SPS) energies within the microscopic transport model. The relation of the reaction zones to the kinetic and chemical freeze-out processes is discussed. It is shown that the space-time freeze-out layer is most extended in time in the central region, while, especially for higher collision energies, the layer becomes very narrow at the sides. The parametrization of freeze-out hypersurface in the form of specific hyperbola of constant proper time was confirmed. The specific characteristic time moments of the fireball evolution are introduced. It is found that the time of the division of a reaction zone into two separate parts does not depend on the collision energy. Calculations of the hadronic reaction frequency show that the evolution of nucleus-nucleus collision can be divided into two hadronic stages. [ABSTRACT FROM AUTHOR]

Abstract: Stump-to-tree spread is a key step in the root and butt-rot disease caused by Heterobasidion annosum sensu lato. In Norway spruce stands, Heterobasidion parviporum is more likely to spread to neighbouring trees from stumps with a large diameter than from small stumps. However, H. annosum sensu stricto does not appear to share this pattern of infection. Given that the ratio of heartwood to sapwood varies depending on the size of the stump, we investigated the role of heartwood and sapwood in stump infection by H. parviporum and H. annosum s.s. To determine whether heartwood–sapwood susceptibility was different in different host species, both Norway spruce and Scots pine stumps were included in the study. Sapwood, heartwood and the border zone between sapwood and heartwood of spruce stumps and the heartwood and sapwood of pine stumps were artificially inoculated with different genotypes of H. annosum s.s. and H. parviporum. Only one zone was inoculated per stump. Infection was assessed 2 and 10months after inoculation at 5 and 30cm below the point of inoculation. On spruce stumps, H. parviporum and H. annosum s.s. were mostly confined to the heartwood. The area infected by H. annosum s.s. was smaller than that infected by H. parviporum. Both sapwood and border infections tended to grow towards the heartwood, whereas heartwood inoculations tended to remain in the heartwood, indicating that heartwood was more favourable for H. parviporum and H. annosum s.s. colonisation in spruce stumps. On pine, heartwood colonisation failed and only H. annosum s.s. was found in the sapwood. Our results suggest a possible association between the size of the stump and the spread of H. annosum s.s. to neighbouring trees mediated by the heartwood content, suggesting that screening for heartwood resistance could be a potentially interesting direction for future research. Treating stumps at final felling would be advisable owing to the large area of heartwood exposed by this operation. [Copyright &y& Elsevier]

This study deals with the impact of the operating conditions, e.g. pressure, preheating temperature, pressure drop across the nozzle, nozzle size and stoichiometry, on the reaction zone location and spray evaporation progress in case of a lifted flame. Lifted flames are highly valued for their NO reduction potential and for their low susceptibility to flash-back and thermo-acoustic instabilities. These advantageous features arise from the improved homogeneity of the fuel-air mixture provided to the reaction zone. One distinctive feature of the lifted flames is the presence of the so called lift-off zone located between nozzle outlet and main reaction zone. Within the lift-off zone fuel and oxidizer remain a certain time in contact and mix together prior to the onset of the combustion reaction. This leads to a more uniform heat release distribution and lowers the nitrogen oxides emissions at lean conditions by reducing the temperature spikes. In contrast to many other studies the subject of investigation was not a plain jet flame, but a modified version of the airblast nozzle, widely used in industrial applications. The nozzle was operated with liquid kerosene. As liquid fuels are easier to handle than gaseous or solid, it is expected that many efforts in the future will focus on the development of liquid fuels surrogates. Our previous investigations have shown, that the nozzle is well suited to be operated with gaseous fuels as well (Fokaides et al, J Eng Gas Turbine Power 130, 011508 ). The position of the reaction zone was determined by means of chemiluminescence of the OH radicals and from its location the lift-off height was derived. In addition the fuel evaporation progress was measured by means of light scattering, revealing that fuel droplets and main reaction zone are well separated. It was found that the operating conditions have a versatile impact on the length of the lift-off zone and spray cone and thus on the degree of pre-evaporation and premixing. Thus, it may be concluded, that through a proper choice of operating conditions and combustor size a desired lift-off height can be adjusted in accordance with criteria, like available space, required emission levels etc. [ABSTRACT FROM AUTHOR]

Copyright of Wood Industry / Drvna Industrija is the property of Drvna Industrija and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Extracts of wound-associated beech wood (Fagus sylvatica L.) were spectrophotometrically analyzed and a paper disc screening test was applied to estimate their fungicidal potential against selected brown (Gloeophyllum trabeum) and white (Trametes versicolor) rot fungi. Colorimetric analysis revealed that higher amounts of total phenols, flavonoids and proanthocyanidins were characteristic of the reaction zone, and especially of wound-wood, while the lowest contents were measured in red heart samples. Estimation of the fungicidal properties of wound-associated wood extracts revealed that the evident inhibitory effect on wood decaying fungi can be ascribed to methanolic extracts of wound-wood, as well as to healthy sapwood. Extracts of reaction zones did not exhibit a corresponding inhibitory effect toward the chosen fungi. These results indicate a potential defensive function of wound-wood and sapwood in living trees, whereas already formed reaction zones behave as physical barriers rather than chemically inhibiting fungal growth. [Copyright &y& Elsevier]

A precise evaluation of the active reaction zone in the electrodes is important to design an effective solid oxide fuel cell (SOFC). A scale analysis and one-dimensional numerical simulations are conducted to obtain a better understanding of the electrochemical reaction zone in a SOFC anode. In the scale analysis, the characteristic lengths of the electron, oxide ion, and gas transports are evaluated from their conservation equations. Relative comparisons of the characteristic lengths show that the transport phenomena in the SOFC anode are primarily governed by the oxide-ion conduction under standard operating conditions. The gas diffusion may affect the extent and the location of the active reaction zone at high temperature and/or low reaction gas concentration conditions. The one-dimensional numerical simulations for an anode provided detailed information such as the electric potential of electron- and ion-conducting phases, the gas concentration, and local charge-transfer current distributions. It is found that the electrochemical reaction actively occurs in the vicinity of the anode-electrolyte interface. The effective thickness increases as the characteristic length of the ion conduction is increased resulting in better power generation performance. The effective thickness is also increased when the gas-diffusion length is short. The cell performance is, however, lowered in this case because the low gas diffusivity yields the increase of the ohmic loss of ion conduction as well as the concentration overpotential. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.20373 [ABSTRACT FROM AUTHOR]

Heterobasidion parviporum, a common pathogenic white-rot fungus in managed Norway spruce forests in northern and central Europe, causes extensive decay columns within stem heartwood of the host tree. Infected trees combat the lateral spread of decay by bordering the heartwood with a fungistatic reaction zone characterized by elevated pH and phenol content. To examine the mode of fungal feeding in the reaction zone of mature Norway spruce trees naturally infected by H. parviporum, we conducted spatial profiling of pectin and hemicellulose composition, and established transcript levels of candidate fungal genes encoding enzymes involved in degradation of the different cell wall components of wood. Colonized inner heartwood showed pectin and hemicellulose concentrations similar to those of healthy heartwood, whereas the carbohydrate profiles of compromised reaction zone, irrespective of the age of fungal activity in the tissue, indicated selective fungal utilization of galacturonic acid, arabinose, xylose and mannose. These data show that the rate of wood decay in the reaction zone is slow. While the up-regulation of genes encoding pectinases and hemicellulases preceded that of the endoglucanase gene during an early phase of fungal interaction with xylem defense, the manganese peroxidase gene showed similar transcript levels during different phases of wood colonization. It seems plausible that the reaction zone components of Norway spruce interfere with both lignin degradation and the associated co-hydrolysis of hemicelluloses and pectin, resulting in a prolonged phase of selective decay. [ABSTRACT FROM AUTHOR]

Abstract: Allocation of photosynthates to defence responses at the expense of biomass increase is a common strategy amongst plants to cope with stress factors. Trees reduce the spread of decay by creating a secondary metabolite-rich reaction zone as fungal ingresses the sapwood. Reaction zone formation implies a sacrificial conversion of sapwood, thus, as decay progresses, the sapwood area of the tree is reduced. The relative contribution that reaction-zone formation and sapwood loss make to radial growth decrease is unclear. To answer this question we reconstructed radial-growth patterns in 100 Norway spruce (Picea abies) trees with a range of reaction zone and sapwood disruption. Basal area increment (BAI) between 1960 and 2007 and its relationship with sapwood reduction and reaction zone formation was assessed using structural equation models (SEM). BAI data showed that over 10years, trees with small or no decay columns (<40%) and a reaction zone shifted from a growth rate that was similar to trees without a reaction zone towards low growth rate similar to trees with large decay columns. The fitted SEM indicated that: (i) the effects of decay on growth would begin with the formation of the reaction zone, and (ii) the smaller sapwood in decayed trees as compared with healthy trees would not reduce radial growth, but would be in part the result of previous periods of low growth due to reaction-zone formation. [Copyright &y& Elsevier]

Results are presented for mineral and petrographic study of chromite-periclase refractories used for obtaining nickel in RNB arc furnaces under ZF AO GMK Noril'sk Nickel enterprise conditions. The nature and mechanism of refractory breakdown during service is revealed on the basis of studying the chemical and phase composition of reaction zones formed in a refractory, and versions are considered for improving their service life. [ABSTRACT FROM AUTHOR]

Abstract: Rotfinder is a non-destructive decay-sensing apparatus based on resistance measurements in standing trees. The accuracy of Rotfinder in detecting decay was evaluated in 500 standing trees in three Norway spruce (Picea abies) plots. Trees were measured at three heights, 0.30, 0.66 and 1.30m. Sections were later inspected for the presence of decay and reaction zones. Inspected trees were mostly infected by Heterobasidion annosum and showed a large variation in the amount of decay present, ranging from 0.1% to 88.0% of the section. Correctly and incorrectly classified trees were compared in terms of ion and element concentration, density and moisture. Measurements at stump level (0.30m) were more accurate than measurements at breast height (1.30m) where the reaction zone and decay columns showed lower moisture content. The accuracy of Rotfinder increased when trees with small decay columns were regarded as ‘non-decayed’. When only trees with more than 15% of the section decayed were regarded as ‘decayed’, Rotfinder had an accuracy of 0.86 when performing assessments at stump level. False negatives, as opposed to true positives, corresponded to trees with smaller and drier decay columns, drier reaction zones and lower K+ (potassium) concentration in the decay column. False positives corresponded to trees with large sapwood and high sodium content in the sapwood. Rotfinder represents an alternative to the standard method of using increment core observations to assess decay in living trees. [Copyright &y& Elsevier]

Results of research work performed by Gruppa Magnezit are provided for prolonging the campaign of a zinc production Waelz kiln. Research into the corrosion resistance of refractory objects by a charge, consisting of ore and coke, is used to select the substance composition and development of technology for chromite-periclase refractory production that is inert towards Waelz material components. Service tests show that use of new refractories within the reaction zone of aWaelz kiln lining provides stable performance for the production process with high productivity and an increase in the time between repairs. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the combustion characteristics of low calorific gas in silicon carbide (SiC) foam. The temperature distribution, reaction zone, maximum temperature, and combustion wave propagation velocity were analysed at different inlet velocities, equivalence ratios of premixed gases, and pore densities. The temperature distribution near the reaction zone was determined by a time-based method. Super-adiabatic combustion was obtained in porous media under different conditions. The experimental results showed that higher temperatures were obtained in SiC foams of 30 pores per inch (PPI) than those measured for foam of 20 PPI. Increased equivalence ratio of premixed gases and pore density led to a thicker reaction zone and a higher preheating efficiency in the preheating zone. The combustion wave propagation velocity, which was less than 2mm/s under these experimental conditions, was increased with increased inlet velocity and decreased equivalence ratio of premixed gases. The combustion wave propagation in foams of 20 PPI had the lowest velocity because of the good match of convection and radiation. [Copyright &y& Elsevier]

wide variety of electric-arc reactors are involved in different areas of science and technologies. Therefore, a demand arose for their systematization. Here we present the classification of most existing types of electric-arc reactors regarding the mutual positioning of plasma-generation and reaction zones. There are three types of reactors: separated, single-chamber, and combined type. Different engineering solutions in each type led to some scatter in the thermal efficiency, power range, lifetime, and other results. No consideration has been given to the reactors of single-chamber heating. They are very special and require individual researches. [ABSTRACT FROM AUTHOR]

Abstract: Beech (Fagus sylvatica L.) branches were topped and after five months the wound response was analyzed by PIXE, 3D-MRI and light microscopy. From freshly cut and deeply frozen sample 30μm thick longitudinal-radial tissue sections were prepared for anatomical investigations and micro-PIXE analysis. Light microscopy revealed the structural response to wounding, i.e. occurrence of the reaction zone between the exposed and dehydrated dead tissue and healthy sound wood. The reaction zone was characterized by tylosis in vessels and accumulation of colored deposits in parenchyma cells, fibres and vessels. 3D MRI of a parallel sample showed that the moisture content in the reaction zone was three times higher than in normal healthy wood. Micro-PIXE mapping at margins of compromised wood in beech revealed an increased concentration of potassium in the reaction zone. The increase in the calcium concentration was associated with the dehydrated tissue adjacent to reaction zones. In addition, micro-PIXE was used to determine the elemental distribution in annual tree rings. This may be relevant for retrospective assessment of environmental pollution in wood by measuring yearly increments as a biomonitoring tool. The analysis of European larch (Larix decidua Mill.) wood revealed a high similarity between optical characteristics (i.e. late versus earlywood) and elemental (e.g. Cl, K, Ca, Mn, Zn) distribution. [Copyright &y& Elsevier]

Lean premixed natural gas/air flames produced by an industrial gas turbine burner were analyzed using laser diagnostic methods. For this purpose, the burner was equipped with an optical combustion chamber and operated with preheated air at various thermal powers P, equivalence ratios Φ and pressures up to p =6 bars. For the visualization of the flame emissions OH* chemiluminescence imaging was applied. Absolute flow velocities were measured using particle image velociinetry (PIV), and the reaction zones as well as regions of burnt gas were characterized by planar laser-induced fluorescence (PLIF) of OH. Using these techniques, the combustion behavior was characterized in detail. The mean flow field could be divided into different regimes: the inflow, a central and an outer recirculation zone, and the outgoing exhaust flow. Single-shot PIV images demonstrated that the instantaneous flow field was composed of small and medium sized vortices, mainly located along the shear layers. The chemiluminescence images reflected the regions of heat release. From the PLIF images it was seen that the primary reactions are located in the shear layers between the inflow and the recirculation zones and that the appearance of the reaction zones changed with flame parameters. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies the effects of the number and location of solid obstacles on the rate of propagation of turbulent premixed flames. A vented explosion chamber is constructed where controlled premixed flames are ignited from rest to propagate past grids or baffles plates as well as other solid obstacles strategically positioned in the chamber. Laser Induced Fluorescence (LIF) is used to image OH which is used as an indicator of the reaction zone while pressure transducers are used to obtain pressure–time traces. Single grids or baffle plates located at different distances from the ignition source are tested. Two as well as three baffle plates are also investigated in varying configurations. It is found that while the peak overpressure increases with increasing number of grids or baffle plates, a limit is reached where the pressure starts to decrease. The location of the obstacles is found to have a significant effect on the overpressure and the flame structure. Higher overpressures are obtained when the baffle plates and obstacles are stacked closer together hence not allowing turbulence to decay. LIF images for OH show that the reaction zones become more contorted with increasing number of baffle plates in the flame path. [Copyright &y& Elsevier]

Host responses, i.e., formation of reaction and barrier zones, were studied in the xylem of Douglas-fir, beech, oak, and sycamore trees, after wounding and artificial inoculation with brown-, soft-, and white-rot fungi. The objective of this study was to determine whether strongly invasive wood-decay fungi trigger a higher magnitude of host response than weakly invasive fungi. Differences in active host response, observed microscopically, depended on wood anatomy. Restriction of discoloration and decay by reaction zones was primarily influenced by the content and distribution of parenchyma cells within the sapwood of each host. By contrast, barrier-zone anatomy showed similarities to the basic xylem structure of each host, except for some cell types that were either reduced in number or absent. Regardless of the decay fungus inoculated, individual trees of each host responded differently. With the exception of beech trees inoculated with the soft-rot fungus Kretzschmaria deusta (Hoffm.: Fr.) P. Martin and the white-rot fungus Trametes versicolor (L.: Fries) Pilát, host response appeared to be nonspecific, as the degree of fungal invasiveness did not influence the magnitude of host response within the xylem of investigated trees. [ABSTRACT FROM AUTHOR]

Abstract: To identify differentially expressed genes of the white-rot fungus Heterobasidion parviporum, two cDNA libraries were constructed using suppressive subtraction hybridization (SSH) technique with RNA extracted from an advanced stage of decay area and from colonization front next to the reaction zone of the stem of a mature Norway spruce naturally colonized by the fungus. Besides several cytochrome P450s and hypothetical proteins with unknown function, the SSH libraries constructed contained, among others, genes involved in basic cellular processes, and lignin and cellulose degradation. To examine the role of selected candidate genes for each functional group, three trees, each colonized by a different genotype of the pathogen and showing a variable degree of wood decay, were used for real-time RT-PCR profiling of candidate genes. In the decay transition areas the study revealed activity centers that showed remarkable similarity in the transcript profiles of the monitored genes. [Copyright &y& Elsevier]

The conversion of biogenic silica (opal-A) to opal-CT (cristobalite and tridymite) in biosiliceous sediment causes increased rates of water expulsion because of the reduction in sediment porosity and dehydration of the amorphous opal-A phase. This release of water occurs over large tracts of sedimentary basins during sediment burial within discrete, diagenetic, reaction zones. Analysis of two-dimensional and three-dimensional seismic data sets from basins in the Northern Hemisphere provides geophysical evidence for a variety of fluid conduits and roughly circular erosional depressions at the contemporaneous seabed. We interpret these features as indicative of water expulsion and focused fluid flow emanating from opal-A to opal-CT reaction zones at burial depths within the range 200-800 m. The rate at which water is expelled depends upon the degree of porosity reduction and the weight fraction of bound water at the reaction zone as well as the rate of advance of the reaction zone. Where the reaction is actively taking place within homogeneous biosiliceous sediment, the rate of water expulsion is independent of the reaction rate. This is because water is released across the entire reaction zone; therefore, slow reaction rates are compensated for by expulsion of water across wider reaction zones. We calculate the rate and volume of water expulsion for the Faeroe-Shetland Basin, where the sediment immediately below the reaction zone contains, on average, ~30% opal-CT by weight. The estimated volumetric rate of water expulsion per unit surface area at the present day is ~6 m³ My-1 per square meter, which is greater than the vertical flux of water at the same depth from compaction of the deeper basin fill. The average volumetric rate of water expulsion is ~120 km³ My-1 across the whole basin. Biogenic silica is particularly rich in Neogene successions in high latitude and equatorial regions, and where silica reaction zones are identified, they should be factored into sediment compaction and fluid-flow histories. [ABSTRACT FROM AUTHOR]

We carried out hydrothermal experiments in the system dolomite-quartz-H2O to track the temporal change in reaction rates of simultaneous reactions during the development of reaction zones. Two types of configurations for the starting materials were prepared: dolomite single crystals + quartz powder + water and quartz single crystals + dolomite powder + water, both sealed separately in gold capsules. Runs at 0.1GPa and 600°C with cold seal pressure vessels gave the following results. (i) In short duration (45–71 h) runs metastable layer sequences involving wollastonite and talc occur in the reaction zone, whereas they disappear in longer duration (168–336 h) runs. (ii) The layer sequence of the reaction zones in short duration runs differs from place to place on the dolomite crystal even in the same run. (iii) The diversity of layer sequences in the short duration runs merges into a unique layer sequence in the longer duration runs. (iv) The reaction zone develops locally on the dolomite crystal, but no reaction zone was observed on the quartz crystal in any of the runs. The lines of evidence (i)–(iii) show that the system evolves from an initial transient- to a steady-state and that the kinetic effect is important in the development of reaction zones. A steady diffusion model for the unique layer sequence Qtz/Di/Fo + Cal/Dol + Cal/Dol shows that the Dol + Cal layer cannot be formed by diffusion-controlled process and that the stability of the layer sequence Qtz/Di/Fo + Cal/Dol depends not only on L-ratios ( a = / LCaOCaO and b = / LMgOMgO) but also on the relative rate P = (−2 ξ1 − ξ2)/(– ξ1 − 2 ξ2) of competing reactions: Dol + 2Qtz = Di + 2CO2 ( ξ1) and 2Dol + Qtz = Fo + 2Cal + 2CO2 ( ξ2). For smaller P the stability field will shift to higher values of a and b. The steady diffusion model also shows that the apparent-non-reactivity on the quartz surface can be attributed to void formation in a large volume fraction in the diopside layer. [ABSTRACT FROM AUTHOR]

Reaction zones of 0.5–10.0 m thick are commonly observed between serpentinite and pelitic schist in the Nishisonogi metamorphic rocks, Kyushu, Japan. Each reaction zone consists of almost monomineralic or bimineralic layers of talc + carbonates, actinolite (or carbonates + quartz), chlorite, muscovite and albite from serpentinite to pelitic schist. Magnesite + quartz veins extend into the serpentinite from the talc + carbonates layer, while dolomite veins extend into the pelitic schist from the muscovite layer. These veins are filled by subhedral minerals with oriented growth features. Primary fluid inclusions yield the same homogenization temperatures (145–150°C) both in the reaction zone and in the veins, suggesting their simultaneous formation. Mass-balance calculations using the isocon method indicate that SiO2, MgO, H2O and K2O are depleted in the reaction zone relative to the protoliths. These components were probably extracted from the reaction zone as fluids during the formation of the reaction zone. [ABSTRACT FROM AUTHOR]

A new process to abate foam-causing micro-organisms of the genus of Nocardia sp. and alike was developed in the Sha Tin Sewage Treatment Works of Hong Kong in 2002 under an in-house research and development study. The new FIONA process relates to a process of inhibiting the growth of the foam-causing micro-organisms of genus Nocardia sp. and alike, which are commonly found in activated sludge sewage treatment process with nutrient removal. The Sha Tin Sewage Treatment Works is the largest secondary sewage treatment works in Hong Kong with nitrogen removal capability. It has been suffering from Nocardia foam since its commissioning in 1982, which had led to consistent non-compliant events. The new process has been put into full scale application since 2002 and its foaming abatement effect is very effective; resulting in resumption of full compliance with the discharge licence since November 2003. The FIONA Process basically comprises a chemical dosing system and a reaction zone with a mean hydraulic retention time of 1 hour. The dosing point of the Process can be at upstream sewage pumping stations as well as the inlet works of the sewage treatment works. The dosing chemicals are to create an anoxic environment in the sewage so as to boost up the removal of the readily biodegradable substrates, which are favourable substrates of the foam-causing micro-organisms, in the sewage prior to entering the bioreactors. In such way, it will help out-compete the foam-causing micro-organisms in the bioreactors. Full scale dosing results in the Sha Tin Sewage Treatment Works from 2002 to 2004 had demonstrated that the previous year-round appearance of the Nocardia foam in the bioreactors had been greatly abated to an extent from little to moderate appearance only from January to April with complete Nocardia foam disappearance from May to December. The dosing chemical being used is calcium nitrate at dosing rates from 15 to 50 mL of aqueous calcium nitrate at 50% concentration by weight (equivalently 50 to 150 mM of calcium nitrate) per m3 of sewage. For other metallic nitrate salts, the nitrate mass content must be equivalent to the nitrate mass of calcium nitrate at the above dosing range. For hydrogen peroxide, it is believed the same effect would occur, however, there is no practical data available. A theory for the FIONA Process based on the bio-selector effect is also proposed albeit further research is necessary for its substantiation. [ABSTRACT FROM AUTHOR]

For a planar detonation wave propagating in the plastic-bonded explosive PBX 9501, measurements of the reaction zone display a classical ZND profile. Moreover, the reaction-zone width is substantially less than the average size of an explosive grain. We show that the reaction zone is compatible with realistic constitutive properties and an Arrhenius reaction rate based on the bulk temperature. Thus, contrary to conventional wisdom, hot spots are not needed to propagate a detonation wave. Conventional wisdom is based, in part, on shock desensitization experiments; the observation that precompressing a PBX with a weak shock – which eliminates voids as nucleation sites for hot spots – can quench a propagating detonation wave. By analysing the temperature behind two shocks compared to a single shock and the corresponding change of the induction time, we show that a detonation wave sustained by the bulk reaction rate from shock heating is compatible with shock desensitization. Shock desensitization depends on having a temperature sensitive rate, which usually is associated with detonation wave instability. However, for PBX 9501 the temperature variation in the reaction zone is small, and one-dimensional simulations show that this results in a stable detonation wave. Furthermore, we show that two additional phenomena are compatible with the perspective that bulk burn can sustain a planar detonation wave: failure diameter, which does depend on the heterogeneous structure of a PBX; and PBXs with a lower HE content which display an irregular detonation front. [ABSTRACT FROM AUTHOR]

Surface-volume reactions occur in many physical systems such as biological and industrial processes. Though traditionally modeled as a surface, the reaction zone is usually a thin layer (often a gel) abutting a flowing fluid or gas. Therefore, one would expect a more realistic model for the reacting zone to include the effects of transport in the gel. In this paper we examine the BIAcore, a device for measuring rate constants which has this geometry. To explain anomalous measurements from the device, it has been proposed that some flow penetrates into the dextran (gel) layer, thus enhancing transport. To analyze the reversible kinetics, asymptotic and singular perturbation techniques are used, yielding linear and nonlinear integrodifferential equations. Explicit and asymptotic solutions are constructed for cases motivated by experimental design. The results indicate that such flow penetration effects are bound to be negligible in surface-volume reactions, regardless of the flow model used. [ABSTRACT FROM AUTHOR]

A reaction zone between a metamorphosed basic dyke and marble at Hirao-dai, north Kyushu, Japan, consists of well-organized sequential zones of diopside, garnet and wollastonite; textures are characteristic of diffusion-controlled structures. The reaction zone formed during contact metamorphism associated with intrusion of a Cretaceous granodiorite at ∼300 MPa and 700 °C. The metamorphosed basic dyke consists of diopside, biotite and plagioclase ( XAb = 0.4–0.8), whereas the marble is almost pure calcite. The initial boundary between the dyke and the marble is probably located within the current diopside zone, as calcite occurs as remnants among diopside grains in areas close to the boundary with the garnet zone. This observation provides a criterion to judge the stability of the zonal sequence in our modelling. The formation of the reaction zone is attributed to a single-stage steady-state process with five overstepping reactions. CaO, MgO, FeO, SiO2 and AlO3/2 are the reaction-controlling components that are necessary to describe the growth of the reaction zone. An isochemical steady-diffusion model cannot reproduce the measured phase ratios of product minerals; this indicates open-system behaviour of the reaction zone. The choice of closure components is an essential task in the treatment of open-system modelling, together with determination of phase ratios (Ashworth & Birdi model) or estimation of boundary fluxes (Johnson & Carlson model). Of all the possible combinations of closure components, closure conditions for CaO and MgO provide the best results for both models. The stability of the zonal sequence is limited at relatively large values of LSiSi/ LCaCa. Similar results from the two models confirm their consistency under the same closure conditions. [ABSTRACT FROM AUTHOR]