Control of dilution using the modified creeping cone method at Selebi North Mine

Mining companies are adopting bulk mining methods in their operations because they are safe and can be easily mechanized and automated. The introduction of the creeping cone method at Selebi North Mine in Botswana reduced ore dilution by a half. However, the low grades of the mineable reserves in the deeper sections of the mine require further reductions in dilution to mine profitably. The modified creeping cone (MCC) method was designed to create stable stope wall conditions and give lower dilution levels. Voussoir arch and simple beam theory methods were used to design the MCC method. The results show that for stopes 50 m high and 4 – 22 m wide, 50 – 185 m of room span can be mined using cable bolt reinforced walls. With the MCC method, ore dilution can be reduced to 19.2% while ore grades will increase by 10.5%.     

Synthesis of Fe based ZrB2 composite coating by gas tungsten arc welding

Abstract

ZrB₂/Fe composite coating was in situ synthesised by gas tungsten arc welding cladding process on AISI 1020 steel. Zr, B₄C and Fe–B alloy powders were used as precursor powders. The phase composition and microstructure were investigated by X-ray diffraction analysis, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Microhardness of ZrB₂/Fe composite coating at room temperature was examined. Main phases obtained from Zr and B₄C precursor are ZrB₂ and α-Fe, and those obtained from Zr and Fe–B precursor are ZrB₂ and FeB. In the upper part of these composite coatings, ZrB₂ phase mainly grows along temperature gradient direction. The middle part of these composite coatings has the highest ZrB₂ content and highest microhardness. Gradient dispersions of ZrB₂ reinforcements appeared in the composite coating from the middle to the bottom, leading to gradient dispersions of microhardness. With decreasing dilution rate, ZrB₂ content and microhardeness increase.     

Continuous production of poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate): Effects of C/N ratio and dilution rate on HB/HV ratio

Ralstonia eutropha was cultivated in a continuous stirred fermenter with various C/N ratios (20, 30, and 40), dilution rates, and organic salt substrates (sodium propionate or sodium valerate) to explore the microbial growth and the poly(3HB-co-3HV) accumulation. When sodium propionate was used as the secondary carbon source, the HB/HV molar ratio at various C/N ratios and dilution rates did not change appreciably (approximately 90: 10). The highest poly(3HB-co-3HV) content in biomass (41.8%) and poly(3HB-co-3HV) productivity (0.100 g/(L·h)) occurred under the condition with a C/N ratio of 20 and dilution rate of 0.06 h⁻¹. When sodium valerate was used as the secondary carbon source, the productivity of poly(3HB-co-3HV) increased with increasing dilution rate for the C/N ratio of 30 and 40. The average HB/HV molar ratio ranged from 48: 52 to 78: 32. The feeding of sodium valerate promoted the accumulation of HV better than feeding sodium propionate did. This study shows that a potential strategy of manipulating by both C/N ratio and dilution rate could be used to control the HV unit fraction in poly(3HB-co-3HV) in a continuous cultivation.     

Probe measurements and numerical model predictions of evolving size distributions in premixed flames

Particle size distributions (PSDs), measured with a dilution probe and a Differential Mobility Analyzer (DMA), and numerical predictions of these PSDs, based on a model that includes only coagulation or alternatively inception and coagulation, are compared to investigate particle growth processes and possible sampling artifacts in the post-flame region of a C/O = 0.65 premixed laminar ethylene-air flame. Inputs to the numerical model are the PSD measured early in the flame (the initial condition for the aerosol population) and the temperature profile measured along the flame’s axial centerline. The measured PSDs are initially unimodal, with a modal mobility diameter of 2.2 nm, and become bimodal later in the post-flame region. The smaller mode is best predicted with a size-dependent coagulation model, which allows some fraction of the smallest particles to escape collisions without resulting in coalescence or coagulation through the size-dependent coagulation efficiency (γ_SD). Instead, when γ = 1 and the coagulation rate is equal to the collision rate for all particles regardless of their size, the coagulation model significantly under predicts the number concentration of both modes and over predicts the size of the largest particles in the distribution compared to the measured size distributions at various heights above the burner. The coagulation (γ_SD) model alone is unable to reproduce well the larger particle mode (mode II). Combining persistent nucleation with size-dependent coagulation brings the predicted PSDs to within experimental error of the measurements, which seems to suggest that surface growth processes are relatively insignificant in these flames. Shifting measured PSDs a few mm closer to the burner surface, generally adopted to correct for probe perturbations, does not produce a better matching between the experimental and the numerical results.     

NO formation of opposed-jet syngas diffusion flames: Strain rate and dilution effects

The NO formation characteristics and reaction pathways of opposed-jet H₂/CO syngas diffusion flames were analyzed with a revised OPPDIF program which coupled a narrowband radiation model with detailed chemical kinetics in this work. The effects of strain rates ranging from 0.1 to 1000 s^?1 and diluents including CO₂, H₂O and N₂ on NO production rates were investigated for three typical syngas compositions. The numerical results demonstrated that NO is produced primary through NNH-intermediate route and thermal route at high strain rates, where the reaction of NH + O = NO + H (R51) also become more active. Near the strain rate of 10 s^?1, the flame temperature is the highest and thermal route is the dominant NO formation route, but NO would be consumed by reburn route where NO is converted to NH through HNO, especially for H₂-rich syngas. At low strain rates, radiative heat loss results in a lower flame temperature and further reduce NO formation, while the reaction of N + CO₂ = NO + CO (R140) become more important, especially for CO-rich syngas. With the diluents, NO production rates decreased with increasing dilution percentages. When the flame temperature is very high as the thermal route is dominant near strain rate of 10 s^?1, CO₂ dilution makes flame temperature and NO production rate the lowest. Toward both lower and higher strain rates, adding H₂O is more effective in reducing NO because R140 and NNH-intermediate route are suppressed the most by H₂O dilution respectively.     

梅山铁矿加大结构参数过渡分段的研究

为实现梅山铁矿开采结构参数从现有的 ( 1 0～ 1 3)m× 1 0m合理过渡到 1 5m× 1 5m ,对影响过渡分段采矿损失、贫化指标的原因进行了分析 ,采用实验室物理模拟、现场定量测定等手段 ,找出了过渡阶段不同分段矿石流动规则 ,实行了采用截止品位放矿的放矿管理办法 ,在生产中获得成功应用。     

A screening method based on UV–Visible spectroscopy and multivariate analysis to assess addition of filler juices and water to pomegranate juices

Consumer demand for pomegranate juice has considerably grown, during the last years, for its potential health benefits. Since it is an expensive functional food, cheaper fruit juices addition (i.e., grape and apple juices) or its simple dilution, or polyphenols subtraction are deceptively used.     

Effect of dilution and cooling rate on microstructure and magnetic properties of Ni base hardfacing alloy deposited on austenitic stainless steel

Abstract

Nickel base Colmonoy 6 alloy finds application in hardfacing of various components made of austenitic stainless steel used in fast reactors. Gas tungsten arc deposited Colmonoy suffers from significant loss in hardness and wear properties due to dilution from the substrate. Magnetic property of the deposit is also influenced by dilution, and variation in magnetic parameters with dilution can be employed for non-destructive assessment of hardness in the hardfaced coating of the finished components. During hardfacing deposition, cooling rate may vary with deposition technique and process parameters. Development of a procedure for measurement of hardness of hardface deposit, irrespective of cooling rate, can prove to be useful for practical application. In the present study, the effect of cooling rate on microstructure, hardness and magnetic parameters of the Ni–Cr–B–Si hardface deposits is evaluated, and for coating cooled at different cooling rates, good prediction of hardness from its magnetic property could be obtained.     

Waste-aware single-target dilution of a biochemical fluid using digital microfluidic biochips

A key challenge in design automation of digital microfluidic biochips is to carry out on-chip dilution/mixing of biochemical samples/reagents for achieving a desired concentration factor (CF). In a bioassay, reducing the waste is crucial because the management of waste droplets is cumbersome and expensive; transporting them to the waste reservoir and washing their pathways to clean contaminated regions and remove the residue left by them may increase assay completion time. The existing dilution algorithms attempt to reduce the number of mix-split steps required in the process but focus little on the minimization of sample requirement or waste droplets. In this work, we characterize the underlying combinatorial properties of waste generation and identify the inherent limitations of two earlier mixing algorithms twoWayMix (Thies et al., Natural Computing, 2008) [11] and DMRW (Roy et al., TCAD, 2010) [12] in addressing this issue. Based on these properties, we design an improved dilution/mixing algorithm (IDMA) that optimizes the usage of intermediate droplets generated during the dilution process, which in turn, reduces the demand of sample/reagent and production of waste. The algorithm terminates in O(d) steps for producing a target CF with a maximum error of $\frac{1}{2^{d+1}}$, where d is the an accuracy level of the desired CF. Based on simulation results for all CF values ranging from $\frac{1}{1024}$ to $\frac{1023}{1024}$ using a sample (100% concentration) and a buffer solution (0% concentration), we present an integrated scheme of choosing the best waste-aware dilution algorithm among four approaches such as twoWayMix, DMRW, REMIA (Huang et al., ICCAD, 2012) [13] and IDMA, for a single target CF. Finally, an architectural layout of a DMF biochip that supports the proposed scheme is designed.     

Extracellular enzyme activities during regulated hydrolysis of high-solid organic wastes

The hydrolysis process, where the complex insoluble organic materials are hydrolyzed by extracellular enzymes, is a rate-limiting step for anaerobic digestion of high-solid organic solid wastes. Recirculating the leachate from hydrolysis reactor and recycling the effluent from methanogenic reactor to hydrolysis reactor in the two-stage solid-liquid anaerobic digestion process could accelerate degradation of organic solid wastes. To justify the influencing mechanism of recirculation and recycling on hydrolysis, the relationship of hydrolysis to the synthesis and locations of extracellular enzymes was evaluated by regulating the dilution rate of the methanogenic effluent recycle. The results showed that the hydrolysis could be enhanced by increasing the dilution rate, resulting from improved total extracellular enzyme activities. About 15%, 25%, 37%, 56% and 92% of carbon, and about 9%, 18%, 27%, 45% and 80% of nitrogen were converted from the solid phase to the liquid phase at dilution rates of 0.09, 0.25, 0.5, 0.9 and 1.8d(-1), respectively. The hydrolysis of organic wastes was mainly attributable to cell-free enzyme, followed by biofilm-associated enzyme. Increasing the dilution rate afforded cell-free extracellular enzymes with more opportunity to access the surface of organic solid waste, which ensured a faster renewal of niche where extracellular enzymes functioned actively. Meanwhile, the increment of biofilm-associated enzyme was promoted concomitantly, and therefore improved the hydrolysis of organic solid wastes.