矿床模型在找矿勘探中的应用

矿床模型表现为矿床的描述性特征和依据地质作用对这些特征所作的解释两部分,前者用作选区准则,后者则反映了选区准则和金属成矿之间的成因联系。模型的建立和使用直接影响矿产的勘查,加拿大金矿勘探的历史即为典型实例。     

Electrostatic beneficiation of gold ores

The authors present encouraging results obtained in separation of the Doyon gold ores when using the electrostatic inverted roof apparatus described by I.I. Inculer et al. (ibid., vol.IA-9, no.3, p.318-23, 1983). The electrification phenomena through combined tribo-electric and inductive charging were studied at various relative humidities. Contrary to expectations, the experimental work showed that the best separations are achieved at relatively high humidities of ~70% or higher. One of the main cost factors in electrostatic beneficiation of minerals is that of drying the material. The lesser drying required of this gold ore may be of considerable economic importance     

Cross Current Dual Aerodynamically Shaped Atomizer Electrostatic Spray Nozzle

Experimental results of a novel method and apparatus for achieving selective deposition on the inside surfaces of an enclosure are presented. An apparatus consisting of two aerodynamically shaped air shear nozzlesa generated a charged dual cloud comprising an insecticide aerosol cloud above and a water aerosol cloud below. Through self-expansion of the cloud by mutual repulsion of the charged particles and image attraction to the wall surfaces, a significantly selective deposition was achieved on the inside surfaces in the upper and lower halves of the enclosure.     

Processing and characterisation of sol-gel glasses and powders in the system TeO2-TiO2

Sol-gel processing routes have been developed for the production of thin films and powders in the system TeO₂-TiO₂ from tellurium and titanium alkoxides. The structure and properties of the resultant materials have been characterised as a function of heat treatment temperature. Pure sol-gel derived TeO₂ thin films are difficult to prepare with good optical transparency due to the presence of organic impurities and/or a highly dispersed metallic tellurium phase when heated at temperatures up to approximately 340°C, with crystallisation to -TeO₂ occurring when the heat treatment temperature is further increased. Additions of TiO₂ were found to retard the crystallisation of the -TeO₂ but promote the formation of other TiO₂ or TiTe₃O₈ phases. However, an optimum composition in the range 0.9TeO₂ 0.1TiO₂ was identified, which allows optically transparent thin films to be prepared with high refractive index and offers the potential for practical device manufacture.     

Electrophoretic deposition of alkaline earth coatings from EDTA complexes

A novel process route combining electrophoretic deposition (EPD) and ethylene-diamine-tetra-acetic acid (EDTA) complexation has been developed and used to produce crack-free coatings of alkaline earth oxides with thickness up to 8 m after heat treatment at 700°C. Aqueous systems were found to be unsuitable for the EPD process due to their high conductivity and the effect of liberated gas evolved on the electrodes, and a non-aqueous based alternative formulation was developed based on methanol (solvent/carrier) and ethanediol (stabiliser) in conjunction with the EDTA complexes to allow the EPD process to be successfully used to deposit porous coatings. The coating process has been investigated by electrochemical impedance spectroscopy (EIS), and is thought to involve a combination of the migration of complexed ions in solution, their precipitation as charged colloidal particles in the vicinity of the anode, followed by their aggregation at, and adhesion to the anode surface. It is believed the process may have application for the low cost deposition of a wide range of porous coatings.     

Modeling and simulation for hybrid electric vehicles. I. Modeling

A model for the hybrid electric vehicle (HEV) powertrain simulation has been constructed with a specific power control strategy for an electric-assisted HEV in parallel configuration. The HEV was built by the University of Tennessee, Knoxville. Experimental procedures and data analysis for characterizing power output from the battery and the auxiliary power unit (APU) are presented. The model is implemented based on the empirical formulation and power control scheme, a power control strategy by means of throttle position. It also incorporates regeneration and regenerative braking for battery capacity recovery. The model allows for real time evaluation of a wide range of parameters in vehicle operation as a HEV, a pure electric vehicle, or as a conventional vehicle.     

Amperometric sensing of ethylene oxide in the gas phase

The sensing device used is based on a porous Pt electrode, which is supported on an ion-exchange membrane and directly exposed to the gas phase. Under acid conditions, ethylene oxide was found to be oxidized on the platinum oxide surface at +550 mV vs MSE, thus enabling its monitoring via the measurement of the associated current. A detection limit of 15 ppb was obtained, based on a signal-to-noise ratio of three, and a linear dynamic range was found up to 100 ppm. The effects of mass transport, humidity, and oxygen on the cell response, as well as the cross sensitivity to other organic vapors and inorganic gases are discussed.     

Supplementation with isoflavonoid phytoestrogens does not alter serum lipid concentrations: a randomized controlled trial in humans

Isoflavonoids are a class of flavonoids that are derived in the human diet mainly from soybean-based foods. The major dietary isoflavonoids, genistein and daidzein, have estrogen-like activity and are classed as phytoestrogens. Because estrogens can lower serum LDL cholesterol and raise HDL cholesterol, the objective of this study was to determine if isoflavonoids could improve serum lipids in healthy subjects. Forty-six men and 13 postmenopausal women not receiving hormone replacement therapy completed a randomized, double-blind, placebo-controlled trial of two-way parallel design and 8 wk duration. One tablet containing 55 mg of isoflavonoids (predominantly in the form of genistein) or one placebo tablet was taken daily with the evening meal. Subjects maintained their usual diet and physical activity, which were unchanged throughout the intervention. Measurement of isoflavonoids and their metabolites in 24-h urine samples provided an assessment of compliance and of isoflavonoid metabolism. Serum total, LDL, HDL and HDL subclass cholesterol, triglycerides and lipoprotein (a) were assessed at baseline and during the last week of intervention. After adjustment for baseline values, no significant differences in postintervention serum lipid and lipoprotein (a) concentrations between groups were identified. Further adjustment for age, gender and weight change did not alter the results. In addition, changes in urinary isoflavonoids were not significantly correlated with changes in serum lipids and lipoprotein (a). Therefore, this study does not support the hypothesis that isoflavonoid phytoestrogens can improve the serum lipids, at least in subjects with average serum cholesterol concentrations.     

Beam-quality changes generated by thermally-induced sphericalaberration in laser cavities

Thermally-induced spherical aberration in Nd:YAG rods is investigated. Attention is concentrated on the so-called “intensity moment formalism” to analyze the beam-quality parameter of the emitted laser beams. A number of resonance conditions that certain beam-shape parameters of any stable laser mode should fulfill are also derived, and a comparison with previously reported numerical results is presented     

The use of microbial tracers to monitor seasonal variations in effluent retention in a constructed wetland

Effluent retention in a constructed wetland was determined using both microbial and chemical tracers. Seasonal variation in effluent retention was the main focus of the study. The biotracers used in the study were the coliphage MS2, a bacteriophage of Enterobacter cloacae and antibiotic resistant endospores of Bacillus globigii. Two separate tracer runs were conducted, Winter high flow (January 2002) and Summer low flow (June 2002). The three biotracers were evaluated simultaneously on both occasions, with the commonly used chemical tracer, rhodamine WT, a bright red fluorescent dye, being evaluated during the final experiment. The Winter tracer run was conducted during a typical Winter storm, with a mean effluent discharge of 4.1 ls(-1). Tracer recovery was 98% MS2, 91% Ent. cloacae phage and 2% endospore. Effluent retention was estimated at between 2 and 4 h at 90% phage tracer recovery. The Summer tracer run was conducted at a typical site operating discharge rate of 0.8 ls(-1). Tracer recovery was 23% MS2, 36% Ent. cloacae phage, 8% rhodamine and 14% for the endospores. Effluent retention was estimated at between 11 and 18 h at 90% of phage tracer recovery. Initial results are encouraging and indicate bacteriophage to have further potential as tracing agents in wetlands.