bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Mixing Melt Treatment and Heat-Treatment on the Microstructure and Wear Resistance of Al-22%Si Alloys
Authors: Li Yuan Dong , He Ming Tao , Hu Shao Hua , Suo Jiang Long , Ma Ying
Published: October 2013

The effect of hypereutectic Al-22%Si alloys prepared by means of Controlled Diffusion Solidification (CDS) followed by subsequent heat-treatment on the microstructure and sliding abrasive wear behaviors is investigated. The results show that the primary silicon morphology, size and distribution can be improved by CDS, especially for the case of liquid-liquid mixing. After heat-treatment, the eutectic silicon can be spheroidized. Under the same load, the wear rates for the identically mixed and heat-treated Al-22%Si alloys are lower than those unheat-treatment, and the wear rate of liquid-liquid mixed and heat-treated Al-22%Si alloy reach its minimum. The wear mechanism of traditional cast Al-22%Si alloy includes adhesive wear and fatigue breaking-off, while the liquid-liquid mixing can effectively restrain flaking on the worn surface and avoid the fatigue breaking-off, the wear mechanism is changed into abrasion wear.
Study on Deformation Characteristics of Composite Lining Structure of Shield Tunnel
Authors: Yang Chun Shan , Mo Hai Hong , Chen Jun Sheng , Hou Ming Xun
Published: October 2013

A three-dimensional refined model of composite lining is built with the example of shield tunnel of Xijiang water diversion project in Guangzhou by using finite element software. Segment opening and steel pile deformation characteristics are analyzed. Necessity of light material and steel pile is detailed explained. The results show that the maximal segment opening of composite lining is 0.361 millimeter. The bolts are in elastic state and not appear plastic deformation, so segment without leakage. Steel pipe strain curve is approximate circular symmetry in whole circle. It is necessary to add light material and steel pile, because they can effectively reduce the stress of concrete and prevent cracking.
The Mechanical Properties of FRP Fabric Steel-Reinforced Concrete Columns
Authors: Zhou Le , Wang Xiao Chu , Zhang Jian Peng
Published: October 2013

The mechanical properties of FRP steel-reinforced concrete columns are discussed. We study the constitutive relation of the concrete, based on the model and the experimental dates for the control the size of affecting parameters. When using the used model, the experimental dates can be reanalyzed and corrected for the intensity correct formula of FRP column. The ultimate bearing capacities of FRP constraint rectangular column use superposition principle to calculate the strength calculation. The ultimate bearing capacity of FRP column is divided into two parts: we conclude the big eccentric bearing capacity calculators formula by the columns bend. Through the study of the column, we concluded that the eccentric loading little eccentric calculation formula of bearing capacity. A case though using the example of this formula is similar with experiments results of the data.
Fabrication of Calcium Sulfate/Tri-Calcium Phosphate Composite Bone Fillers through Molding Method
Authors: Sun Hong , Wu Tao , He Yong Qiang , Gong Qiao Juan , Yao Chen Zhong , Gao Jian Ping
Published: October 2013

Calcium sulfate/tri-calcium phosphate (CaSO4/TCP) composite bone fillers were fabricated through molding method. Their structure and properties were characterized by infrared spectroscope, scanning electronic spectroscope, x-ray diffraction and degradation test. The results show that TCP crystals were attached to the CaSO4crystals and prevented the growing of sulfate crystals. So their size is shorter than that of CaSO4crystals prepared from pure CaSO4semihydrate, and some even had defect. The resorption rate of CaSO4bone fillers was decreased when TCP was incorporated.
Preliminary Researches on Possibility of Several Kinds of Plants Including Dracaena Angustifolia Used to Relieve the Damages Caused by Organic Phosphorous Compounds
Authors: Chen Kang Jie , Zhao Gan , Wu Shao Cong , Zhuang Qin Chuan , Qian Fang
Published: October 2013

The leaf extracts ofTaxus chinenwsis var.mairei Cheng et L.K.andAlsophila podophylla Hook.could inhibit respectively the activity of cholinesterase slightly,but leaf extract ofCyrtomium fortunei J. Sm.andDicranopteris dichotoma (Thunb) Bernhshowed little effects on the activity of cholinesterase respectively. The leaf extract of the plants below could activate the activity of cholinesterase evidently by the order asDracaena angustifolia>Sansevieria trifasciata Prain var. laurentii (De Wildem.) N. E. Brown>Piper betle Linn>Duranta repens cv. Dwarf Yellow>Podocaarpus macrophyllus (Thunb.)D. Don>Podocarpus nagi Decussocarpus nagi, the plants may be used to develop new reactivators of ChE inhibited by organic phosphorous compounds.
Preparation and Characterization of Hexadecane Microcapsule Phase Change Materials by In Situ Polymerization
Authors: Song Xiao Qiu , Li Yue Xia , Wang Jing Wen
Published: October 2013

Hexadecane microcapsule phase change materials were prepared by the in-situ polymerization method using hexadecane as core materials, urea-formaldehyde resin and urea-formaldehyde resin modified with melamine as shell materials respectively. Effect of melamine on the properties of microcapsules was studied by FTIR, biomicroscopy (UBM), TGA and HPLC. The influences of system concentration, agitation speed and mass ratio of wall to core were also investigated. The results indicated that hexadecane was successfully coated by the two types of shell materials. The addition of melamine into the urea-formaldehyde resin microcapsule reduced microcapsule particle size and microencapsulation efficiency. The influences of factors such as system concentration, agitation speed and mass ratio of wall to core to different wall materials microcapsules presented different variety trends of the microcapsule particle size.
Application of New Building Materials in Green House
Authors: Liu Yan
Published: October 2013

Green house not only means to make green by planting trees, flowers, etc, it should be follow the basic ideas of people oriented, resource saving and environmental protection. The selection of building materials is a vital aspect in green house. This article starts from the requirements in green residential construction, then discusses in detail about the current situation of new building materials and their future development trends, such as new materials for wall, new insulation materials, new water-proof materials, and new decoration materials and so on.
Improvement of Adsorption Performance Based on Metal Ion Modified ETS-4 Molecular Sieves
Authors: Song Li Yun , Liu Xiao Jun , Zhan Zong Cheng , He Hong , Zi Xue Hong , Qiu Wen Ge
Published: October 2013

Titanosilicate ETS-4 with the Sr and Ni cations modification were prepared by hydrotherrmal method using titanium trichloride and tetraethoxysilane as raw materials. The properties and morphology of the materials were characterized by XRD, SEM techniques, Sr and Ni introduced to the molecular sieve affected the frame contraction when they were heated, and did little effect on the crystallization and morphology. N2and CH4isotherms of each sample were measured at room temperature. The Sr and Ni doping could improve the N2and CH4adsorption capacities of ETS-4. The capacities of the two gases increased in the pressurization process for ETS-4-Sr and ETS-4-Ni, with the pressure increasing, no significant change in capacities of N2and CH4was observed over the ETS-4 sample. Compared to ETS-4 molecular sieves, the capacity for N2of ETS-4-Sr and ETS-4-Ni at the pressure of 1200 mmHg increased 4.2 and 3.9 times, respectively. At last, the results indicated that the cations doping (Sr2+and Ni2+) can improve the adsorption performance of ETS-4 greatly.
Higher-Order Elasticity Constants of Carbon Nanotubes
Authors: Gao Bin , Sun Yu Zhou , Li Shen
Published: October 2013

In this paper, the higher-order elasticity constants are evaluated in the theoretical scheme of higher-order continuum. A single-walled carbon nanotube is treated as a higher-order continuum cylindrical tube with a thin wall, and the representative cell is chosen as a triangle unit that contains four carbon atoms. The Brenner potential is employed to describe the C-C atomic interaction, and the higher-order constitutive relationship is derived by virtue of the higher-order Cauchy-Born rule. The higher-order elasticity constants of carbon nanotubes are evaluated based on the derived higher-order constitutive model, which can provide a foundation for the further analysis of the mechanical properties of carbon nanotubes in the theoretical scheme of higher-order continuum.
Effect of Conductive Silicone Rubber Fillers on Piezoresistive Properties
Authors: Zhang Yue Xian , Li Bin
Published: October 2013

Through the preparation of conductive silicone rubber samples, and the study of its electrical characteristics, this paper expounds the conductive silicone rubber composites relationship between the resistance and applied pressure. It discusses the main influencing factors of the piezoresistive effect. It studies conductive silicone rubber in four different conductive particles as well as the piezoresistive behavior of blending with a variety of fillers. It analyzes conductive silicone rubber samples after adding nanometer material of the piezoresistive properties. The study shows that blending with a variety of appropriate fillers material can improve the linearity of the piezoresistive relationship of the conductive silicon rubber and effectively expand the resistance variable range.
Honeycomb Shaped Monolithic Fe-β Zeolite Catalyst for N2O Decomposition
Authors: Li Ying Xia , Chen Jian , Luo Zheng Lan
Published: October 2013

Honeycomb shaped monolithic Fe-β zeolite catalyst for N2O decomposition prepared by direct extrusion method was investigated. In this paper, we optimized the parameters of the molding process and studied the decomposition properties of the honeycomb catalysts. Monolithic materials could be extruded successfully only with the plasticity ranging from 0.177 to 0.473. The content of SB powder, nitrate and water was shown to have a significant influence on the mechanical strength of the extruded materials. The monolithic samples were characterized by using XRD. Catalytic performances of various monolithic zeolites with diverse density (49 cells/in.2, 81cells/in.2, 169 cells/in.2) were thereafter studied. As shown from the result, catalyst activity increased significantly with the increase of monolithic catalyst density.
The Novel Fluid Loss Additive ANMG1305 for Oil Field Cementing
Authors: Liu Xin Xin , Xiao Wen Fa , Xiao Qiang , Dong Li Tao
Published: October 2013

Fluid loss additive is the main component of the cementing fluid. This article use monomer the monomers of 2-acrylamido-2-methyl-propanesulphonic acid (AMPS) and N, N-dimethyl acrylamide (DMAA) by the method of aqueous solution polymerization to synthesis the novel fluid loss additive ANMG1305. Discuss the amount of initiator, the molar ratio of monomer, reaction temperature, which the influence on the properties of the polymer. Through the infrared spectrum, thermo-gravimetric analyzer, viscometer, such as instrument on its microstructure and properties were characterized. We know that all the monomers are involved in the reaction and the polymer has an excellent thermal stability though the microstructural characterization and application performance of the novel fluid loss additive.
The Fabrication of Screen-Printed Lanthanum Hexaboride Films Applied in PDP Protective Layer
Authors: Deng Jiang , Zeng Bao Qing , Wang Xiao Ju , Lin Zu Lun , Qi Kang Cheng , Cao Gui Chuan
Published: October 2013

In this paper, a screen-printed LaB6discontinuous film is coated on the MgO protective layer to meet the market for low power requirement of AC PDP. The surface appearance, optical transmittance and conductivity properties of the screen-printed LaB6/MgO double protective film are studied by changing the slurry contents and annealing temperature. It is found that when the mass ratio of LaB6powder in the printed slurry is 1%, the transmittance of the film is above 90% with excellent insulation properties. The SEM shows that LaB6particles are randomly distributed on the smooth MgO layer surface and distances among LaB6islands are at least several micron dimensions. Besides, XRD patterns indicate that when the annealing temperature is 500°C, the LaB6film exhibits a strong preferred orientation to the (100) plane, which is beneficial to improve the performance of AC PDP.
Studies on the Temperature Difference of a Component under Different Heat Sources
Authors: Luo Hui Fu , Yuan Wei Guo
Published: October 2013

After the description of finite element model of three-dimensional heat conduction, the software FLOEFD is used to simulate a components temperature fields under various heat sources, to get the temperature difference curves and to analysis the difference between them. It comes out that when the power of heat source changes as a triangular curve, corresponding temperature difference is lower than that of sinusoidal power curve, but larger than that of constant power; Change rate of temperature difference of triangular power curve is lower than that of sinusoidal and constant power, but larger than that of square power curve. The distinction of temperature difference is caused by the different change-rate of inputting heat; the distinction of changing rate of temperature difference is caused by the different changing rate of heat source power.
Synthesis and Liquid Crystalline Properties of New Chiral Monomers and Polysiloxanes
Authors: Hu Jian She , Liu Yi Nan , Song Ya Ting , Wang Di
Published: October 2013

To study the structure-property relationships of new chiral liquid crystalline materials based on menthol and explore their potential applications, a monomer 4-(4-allyloxybenzoyloxy) phenyl-4-menthyl-oxyacetyloxybiphenyl-4-carboxylate (LCM) and the corresponding homopolymer (LCP) were synthesized. The chemical structure was characterized by FT-IR and 1H NMR. The liquid crystalline properties were investigated by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X-ray diffraction. The monomer LCM formed a cholesteric phase when a flexible linkage chain was inserted between the mesogenic core and the terminal menthyl groups by reducing the steric effect. The homopolymer LCP exhibited a batonnet texture of a smectic A phase.
Arc Erosion and Morphological Characters of Ag/LSCO(12) Contacts by Different Methods
Authors: He Qing , Yang Hui , Chen Law Son , Fan Xian Ping , Shen Qian Hong , Wu Xin He , Mu Cheng Fa , Zhang Ling Jie
Published: October 2013

To diagnose the arc erosion type and improve arc erosion resistance of Ag/LSCO (Ag/La0.5Sr0.5CoO3-δ) contacts, making and breaking experiments were carried on Ag/LSCO(12) contacts prepared by both traditional powder metallurgy method and a modified one in this work. Arc erosion and morphological characters of this two kinds of Ag/LSCO(12) samples were investigated and the erosion mechanisms were also discussed. The results are that seven types of arc erosion morphologies of Ag/LSCO(12) contacts were classified as the lump region, the cauliflower region, the framework structure, holes and cavities, cracks, spongy region and the vestiges of fusant spreading. There are intrinsic links between these morphological characters. The spongy regions and vestiges of fusant spreading on the contact surface of Ag/LSCO(12) prepared by the new method indicates that its resistance to arc erosion is superior to the contacts prepared by traditional method.
An Inverse Heat Transfer Problem about Crack of Boiler Furnace Wall Based on Infrared Thermographic Temperature Measurement
Authors: Zhou Guo Qiang , Yang Li , Lv Shi Gui , Liu Li Li
Published: October 2013

A three-dimensional physical and mathematical models of the heat transfer in the furnace specimen with an internal defect were established. Combined with the theory of infrared thermographic temperature measurement, using the L-M method, the inverse heat transfer problem of the boiler furnace wall bricks with crack was investigated. The size of defect was accurately estimated. Conclusions can be drawn by computational analysis, firebrick played a major role in the furnace thermal insulation effect. When firebrick fails, the inspection surface temperature is abnormal, and the temperature difference between the outer surface of the defect and that of the normal wall is an exponential relationship with the increase of defect depth.
The Raw Material Sources and Nondestructive Identification Study of the Blue and White Porcelain Made in Jiajing Official Kiln and Dehua Housuo Kiln
Authors: Li Rong Wu , Chen Gin , Yang Da Wei , Zheng Jiong Xin , Chen Li Fang , Cheng Huan Sheng
Published: October 2013

In order to study the raw material sources and their identification methods of blue and white porcelain made in Jingdezhen Jiajing official kiln (J-O-kiln) and Dehua Housuo kiln (D-H-kiln), 22 blue and white porcelain samples of J-O-kiln and D-H-kiln were analyzed for their body and glaze chemical compositions by Proton Induced X-Ray Emission (PIXE). A set of fingerprint chemical components among them were selected for distribution analysis. Our results show that the raw material sources the porcelain bodies of J-O-kiln are relatively concentrated, and those of D-H-kiln porcelain bodies are relatively scattered, and the raw material sources of porcelain bodies made in the two kilns are quite different, and the raw material sources, recipes of the transparent glazes and blue and white glazes made in these two kilns are also quite different. Therefore, blue and white porcelain samples from J-O-kiln and D-H-kiln can be better easily differentiated by PIXE and fingerprint chemical components distribution analysis.
Properties of Grouting Mortar Modified with Alunite/Bauxite/Gypsum Ternary System as Expansion Component
Authors: Dai Yin Suo , Ding Jian Dang , Tan Yue Hu , Yuan Xiao Jun , Lu Chun Hua , Gong Zi Ming
Published: October 2013

The ettringite results from alunite/bauxite and gypsum which has the characteristic of fast setting and volume expansion, so the main properties and microscopic structure of grouting material modified with alunite/bauxite and gypsum at different proportion were investigated. The results have shown that the grouting mortar modified with 7-20% content of bauxite/alunite/gypsum had the properties such as the setting time could be controlled below 1 hour, long-term expansion rate stabilized basically as 0.2%, compressive strength of 1, 3 and 14 days were more than 17 MPa, 31 MPa and 50 MPa, respectively; the pullout force of 1 meter sample at 14 days reached 87 kN. The micro-analyzing by using MIP, SEM and XRD showed that there were plenty of expansive crystals and tiny pore structures in harded paste which can exist steadily for a long term. The achievements will provide an important basis to application of cement-based grouting material as first-aid repairing.
The Redistribution of Electrons in La1-xSrxCoO3 Induced by Distortion of CoO6 Octahedron
Authors: Liu Hao , Zhang Hong Guang , Li Yong Tao , Dong Xue Guang , Chen Yuan Yuan , Chen Ling Shan , Chen Kai , Hou Qing Teng , Ge Xiao Peng , Li Qi
Published: October 2013

The La1-xSrxCoO3(x=0.0, 0.1, 0.2 and 0.3) samples were prepared by solid-state reaction method. The X-ray diffraction patterns show that the samples are ofR-3cspacegroup and the relative intensity of (024) plane diffraction peak increases with the increase of Sr concentration. The x-ray absorption fine structure data of Co ions can be fitted with 2 and 3 different scattering paths for the samples withx=0, 0.1 and forx=0.2 and 0.3, respectively. A new peak arises in x-ray absorption spectra of O ions. These results suggest a relationship between the variations of electron densities and local structure distortion. Both the valence band photoemission and x-ray absorption spectra indicate the existence of possible phase separation scenario that comes from the different types of Co-O bonds which coexist in one sample.
A Study of the De-Noising Methods for Cotton Fabric Rubbing Sound Signal
Authors: Wang Hong Shan , Xu Wei Lin
Published: October 2013

In order to get clear cotton rustling sound signal, which will be analyzed to provide information at a certain stage of fabric processing for developing cotton products, before analysis of the data, it is the need for de-noising processing. The two de-noising methods, the median filtering method and the wavelet method are proposed in this paper. Their principles and algorithms are described. The cotton sound signals are exposed to interference and influence of some kinds of noise signal in the process of the data measured. So in practical applications, the two de-noising methods are used to process cotton rustling sound. The results of the process show the methods of processing the cotton sound signal are effective. The clear signal is getting to the next research.
Galactose as Inducer of the Production of Extracellular Polymeric Substances by Acidithiobacillus ferrooxidans
Authors: Saavedra Albert , Pavez Beatriz , Diaz Mauricio , Gentina Juan Carlos
Published: October 2013

The presence of extracellular polymeric substances (EPS) is important in the building of biofilms on mineral surfaces, increasing the bioleaching activity, as well as protecting the cells from adverse environmental conditions. The objective of this work was to study the effect of galactose in EPS production byAcidithiobacillus ferrooxidans. The experiences were performed in shake flask of 250 mL at 30 °C, 200 rpm and at an initial pH of 1.8. In order to establish the natural tolerance of the strain, its growth behaviour was evaluated at high ferric iron concentrations by adding consecutively the equivalent of 9 g/L of ferrous iron each time it was depleted in the broth. Cell growth stopped once ferric iron concentration increased up to 38 g/L. In order to determine the optimal conditions for EPS production, experiments were run in a chemostat of 0.5 L, operated at a constant dilution rate of 0.03 h-1. Different steady states were obtained varying feeding concentrations of galactose (0.15%; 0.25% and 0.35%) and carbon dioxide (180 ppm and 360 ppm). , Cells grown in the chemostat at optimum operation conditions were used as inoculum to determine oxidative capacity of the microorganisms overproducing EPS. The EPS was quantified using confocal laser scanning microscopy (CLSM), labelling the cells with propidium iodide and EPS carbohydrates with wheat germ agglutinin (WGA). The higher volume production of EPS was observed in cells grown using 360 ppm of CO2and 0.35% of galactose. Also it was observed a size increment of cells, compared to cells grown in culture medium having 9 g/L of ferrous iron where presence of EPS was no detected. The results revealed that EPS overproducing A. ferrooxidansshowed a tolerance to ferric iron concentration almost 9.5 g/L higher than the natural tolerance of cells grown in absence of galactose. Presence of galactose in culture medium stimulated the EPS production.
Thiol-Rich Proteins Play Important Role in Adhesion and Sulfur Oxidation Process of Acidithiobacillus ferroxidans
Authors: Peng An An , Xia Jin Lan , Liu Hong Chang , Zhu Wei , Zhang Rui Yong , Zhang Cheng Gui , Nie Zhen Yuan
Published: October 2013

The proteomics of the extracellular proteins (EPs), outer membrane proteins (OMPs) and the periplasmic proteins (PPs) ofAcidithiobacillus ferrooxidansATCC 23270 grown on Fe2+and S0substrates, respectively, were comparatively studied. 39 expression up-regulated proteins (including 13 EPs, 9 OMPs and 17 PPs) were identified and 70% of them contain cysteine residues in sequence. Some of the selected proteins especially the EPs contain abundant of the cysteine residues and one or more-CXXC-functional motifs. The thiol groups on theAt. ferrooxidanscell surface were selectively marked by Ca2+and SR-μ-XRF mappingin situobservation revealed that the number of thiols on the surface of the cells grown on S0was about five times as that grown on Fe2+substrate. When 0.01 g/L surfactant Tween-80 was added in the S0culture medium, the adsorption and activation related EPs were down-regulated and the sulfur metabolism related proteins was up-regulated. The same phenomenon was observed when the cells were grown on the more easily adhesion sulfur allotrope μ-S. It indicates that the thiol-rich proteins played important roles in adhesion and sulfur oxidation process ofAt. ferrooxidans.
Microbiological Communities in Two Acidic Mine Pit Lakes in the Iberian Pyrite Belt (IPB), Spain
Authors: Falagán Carmen , Sánchez-España F.J. , Johnson D. Barrie
Published: October 2013

The microbiology and geochemistry of two pit lakes at former metal mines (Cueva de la Mora and Guadiana) located in the Iberian Pyrite Belt in Spain were investigated. Both lakes are meromictic, with more acidic and oxidized mixolimnion zones overlying anoxic monimolimnion zones, and transitional chemoclines with characteristic sharp pH and redox potential gradients. Stratification in the pit lakes was reflected in the size and diversity of the microbial communities in the different zones, with the chemocline of Cueva de la Mora pit lake and the hypolimnion (the lower layer of the mixolimnion) in the Guadiana pit lake containing the most complex and abundant microbial communities. Acidophiles that oxidize and reduce both iron and sulfur co-exist within the chemocline/hypolimnion zones, implying that biogeochemical cycling of these two elements is most intense within these layers of the pit lakes. Novel species of bacteria were detected using molecular techniques and, in some cases, isolated and partially characterized. The latter included a novel acidophilic iron-reducing gammaproteobacterium (Acidibacter ferrireducens)
Microbial Ecology in Extreme Acidic Pit Lakes from the Iberian Pyrite Belt (SW Spain)
Authors: González-Toril Elena , Santofimia Esther , López-Pamo Enrique , Omoregie Enoma O. , Amils Ricardo , Aguilera Ángeles
Published: October 2013

Abstract. In mining areas in which sulfur-containing ores are exposed, the oxidation of sulfides leads to the formation of acidic mine drainage (AMD) waters. Both traditional and molecular microbial studies have shown that chemolithotrophic sulfur- and iron-oxidizing bacteria are responsible for this activity. The Iberian Pyrite Belt (IPB), located in southwestern Spain represents one of the world’s largest accumulations of mine wastes and AMD waters. Mineralogical and textural characteristics of the IPB ores favor the oxidation and dissolution of pyrite and the subsequent formation of AMD waters. Acidic pit lakes in the IPB are a hotspot for this activity. These pit lakes are former open pit mines where ores have been exposed leading the formation of AMD waters. At present, there are more than 25 of these pit lakes between the provinces of Huelva and Seville (SW Spain). This work reports the physical properties, hydrogeochemical characteristics, and microbial diversity of two pit lakes located in the IPB Nuestra Señora del Carmen (NSC), and Concepción (CN). Both pit lakes are acid (pH 2-4) and showed chemical and thermal stratification with well defined chemoclines. One particular characteristic of NSC is that it has developed a chemocline very close to the surface (2 m depth). Microbial community composition of the water column was analyzed by 16S and 18S rRNA gene cloning and sequencing. The microorganisms detected in NSC are characteristic of acid mine drainage (AMD), including iron oxidizing bacteria (Leptospirillum) and facultative iron reducing bacteria and archaea (Acidithiobacillus ferrooxidans, Actinobacteria, Acidimicrobiales, Ferroplasma) detected in the bottom layer. Diversity in CN was higher than in NSC. Microorganisms known from AMD systems (Acidiphilium,AcidobacteriaandFerrovum) and microorganisms never reported from AMD systems were both identified.
BioSigma Bioleaching Seeds (BBS): A New Technology for Managing Bioleaching Microorganisms
Authors: Martínez Patricio , Parada Pilar
Published: October 2013

In Bioleaching, although it is already prove that chalcopyrite can be dissolved by microorganisms, a major task is to do it efficiently in economical terms at industrial scale. BioSigma Bioleaching Seeds (BBS) represents a biotechnological breakthrough for the production of bioleaching solutions on demand with high concentrations of biomining microorganisms. This innovation is mainly a product based on the encapsulation of BioSigma bioleaching microorganisms in a natural matrix of alginate. This technology gives the following operational advantages: 1. High concentration of inoculum. 2. Long period of inoculum storage (more than 1 year). 3. Reduction of volume and costs of transport of bioleaching solutions. 4. Homogeneous mineral inoculation; uniform inoculation of the ore using solid capsules. 5. Protection against toxic elements to retain the viability and activity of the bioleaching solutions. 6. Addition of additives for incorporation of nutrients or other molecules that enhance the activity. 7. Encapsulation of different bioleaching microorganisms producing specific "bioleaching seeds" for each biohydrometallurgical process. All the above advantages make this new technology a very attractive alternative to enhance bioleaching processes at on site operations and overcome stressful conditions for biomining microorganisms.
Copper Recovery by Bioleaching of Chalcopyrite: A Microcalorimetric Approach for the Fast Determination of Bioleaching Activity
Authors: Krok Beate , Schippers Axel , Sand Wolfgang
Published: October 2013

Low grade copper ores containing chalcopyrite are increasingly used for copper recovery via biomining. Since metal sulfide oxidation is an exothememic process, bioleaching activity can be measured due to the heat output by microcalorimetry, which is a non-destructive and non-invasive method. The bioleaching activity of pure cultures ofSulfolobus metallicus,Metallosphaera hakonensisand a moderate thermophilic enrichment culture on high grade chalcopyrite was evaluated. Chalcopyrite leaching by microorganisms showed a higher copper recovery than sterile controls. Chemical chalcopyrite leaching by acid produced heat due to the exothermic reaction, the heat output was increased while metal sulfide oxidation by microorganisms.
Dynamic Evolution of the Microbial Community in BIOX Leaching Tanks
Authors: van Hille Robert P. , van Wyk Nathan , Froneman Tamlyn , Harrison Susan T.L.
Published: October 2013

Laboratory scale (7 L) reactors, inoculated with the L. ferriphilum dominated BIOX inoculum, were used to test the stability of the community under controlled conditions. Further, the effect of increased temperature, solids loading and pH fluctuations on the bioleaching performance and community structure were studied. Both performance and community structure remained stable under controlled conditions (41.5°C, 20% solids loading, 7 day residence time). Increasing the solids loading to 31% did not significantly affect performance or community structure. An increase in temperature (2°C every 10 days) did not have a significant effect up to 48°C, but the increase from 48°C to 50°C resulted in the loss of L. ferriphilum and a decrease in leaching performance. A more gradual increase (1°C increments) from 48°C to 50°C resulted in a stable community, dominated by Ac. cupricumulans and Acidithiobacillus caldus. A similar shift in community structure was observed when the pH fell below pH 0.8, but this was transient and L. ferriphilum recovered dominance upon adjustment to a pH > 1.0. A further increase in temperature to 52°C resulted in the loss of At. caldus and the emergence of Sulfobacilli. However, leaching performance under these conditions was poor, despite the presence of over 10 g/L ferric iron. In addition, yeast extract was required to maintain high cell numbers at 52°C. This work has identified a selection of conditions under which the community in BIOX reactors could evolve dynamically towards those communities currently observed in commercial operations.
From Mesophilic to Moderate Thermophilic Populations in an Industrial Heap Bioleaching Process
Authors: Soto Pamela , Acosta Mauricio , Tapia Pierina , Contador Yasna , Velásquez Antonio , Espoz Cristian , Pinilla Carlos , Galleguillos Pedro A. , Demergasso Cecilia
Published: October 2013

A comprehensive monitoring program by culturing and molecular techniques, physicochemical analysis plus the record of the operational conditions have been performed at an industrial bioleaching process for run-of-mine (ROM) material at Escondida mine since 2006. The data collected have been systematized in a data base to allow further analysis for advancing the understanding of commercial bioheap applications. The microbial succession during a heap bioleaching cycle has been formerly described by means of the analysis of the data obtained from the first lift of the industrial process. Data visualization techniques were used to analyze the information and to find patterns in the data. When only the first and second floor of the heap was operative, the mesophile population, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, was predominant in the microbial community. After the start of the third lift operation, a relevant change in the abundance of the moderate thermophile population was evident. Leptospirillum ferriphilum (optimum temperature 35-39°C) and Sulfobacillus thermosulfidooxidans (optimum temperature 45-50°C) became the most abundant microorganism. In addition, the specific iron oxidation activity showed by the moderate thermophilic dominated community is higher than the mesophilic dominated one. A patched distribution of Sulfolobus allowed us to infer the temporal occurrence of small niches with temperature over 50°C inside the heap. The temperature turned out to be a key factor driving the dynamic of the microbial community mainly after the start of the third lift. That shift had a relevant impact on the metallurgical performance of the industrial process.
Impact of the Hydraulic Retention Time on the Performance of a Sulfidogenic Bioreactor
Authors: Klein Robert , Schlömann Michael , Zeng Yun , Wacker Bernd , Glombitza Franz , Janneck Eberhard , Mühling Martin
Published: October 2013

Treatment of acidic Fe (II)- and sulfate-rich mine waters represents a major problem in many areas of the world. Therefore, a process was developed which utilises naturally occurring sulfate-reducing microorganisms for the elimination of sulfate and of part of the acidity from the acidic mine water. In order to improve the performance of this biological sulfate reduction process an in-depth analysis of the microbial diversity and activity in dependence of the hydraulic retention time (HRT) and other process parameters used to run the bioreactors was undertaken. This comparison demonstrated a positive correlation between shorter HRT and increasing sulfate reduction rates. The improvement in performance with decreasing HRT was paralleled by an increase of the total enzymatic activity (measured as hydrolase activity) of the microbial community and of the biomass (measured as protein concentration) in the bioreactors. A partial taxonomic identification of the microbial community in the bioreactors was achieved via nucleotide sequence analysis of a clone library of PCR-amplified 16S rRNA gene fragments prepared from a sample of the microbial biofilm in the bioreactor. Additionally, the genetic fingerprint technique T-RFLP was used to assess temporal changes of the microbial community in the biofilm within the reactor.
Investigation of the Effect of pH Operating Conditions on Bioleaching of Low-Grade Chalcopyrite in Column Reactors
Authors: Tshilombo Odilon M. , Ojumu Tunde V.
Published: October 2013

Bioleaching of low-grade sulphide minerals is now an established process, with much interest in chalcopyrite. However few studies have been carried out on ores containing silicates gangue materials. Chalcopyrite has been reported to be refractory at ambient temperature. Several factors that influence bioleaching kinetics are well documented such as particle size, pH, temperature, galvanic interaction and microbial activity. The purpose of this research was to investigated the effect of pH as well as pre-leaching on bioleaching of silicate rich and low-grade chalcopyrite using mixed thermophilic cultures, with a view to maximize copper solubilization rate in a column reactor operated at 70°C. The column was packed with low-grade chalcopyrite of the size range -20+15 mm. Leaching was monitored at specific time intervals (3 days) by measuring the pH, the redox potential, the copper and iron concentration in the solution. The results of the investigation have shown that copper extracted was highest at pH 1.3 and at moderately low redox potential (410 – 430 mV) using Ag/AgCl electrode, and that pre-leaching contributed insignificantly to the leaching rate. At pH 2.5, the copper extraction was low due to the jarosite. Furthermore, the analysis XRD of leached residues has indicated that the main passivating products were gypsum, jarosite, hexahydrite, and silica. However, although low pH resulted to high copper recovery, the results also showed that the pregnant leach solution (PLS) contained high concentrations of dissolved ions which might have inhibited the microbial activities.
Pretreatment of Refractory Gold Ores Using Cell-Free Extracts of P. chrysosporium: A Preliminary Study
Authors: Ofori-Sarpong Grace , Osseo-Asare Kwadwo , Tien Ming
Published: October 2013

The fungus Phanerochaete chrysosporium has been proven to biotransform refractory gold ores, leading to increase in gold recovery. This transformation has been attributed to enzymes secreted by the microbe. This paper reports the findings of preliminary investigations aimed at assessing the use of hydrogen peroxide and cell-free extracts from the fungus, P. chrysosporium, to effect biotransformation of sulphidic refractory gold ores. The investigations show that the total dissolved arsenic, iron and sulphur in solution were up to 5.2 wt%, 0.9 wt% and 6.0 wt% respectively from flotation concentrate after 72 hrs of treatment. Analysis for sulphide sulphur in the residual solids of the gold concentrate indicated about 25 wt% oxidation within 24 hours of treatment. In general, cell-free decomposition of the samples did not increase beyond 24 hours of contact time, possibly due to exhaustion of the active components. Gold extraction by cyanidation increased by 24% after 24-hr treatment with the cell-free extracts. Comparatively, cell-free (in vitro) treatment recorded 66% overall gold recovery as against 61% for whole cell (in vivo) after 72 hours of treatment. These initial results indicate clearly that in vitro processing is a promising alternative to in vivo processing of refractory gold ores using P. chrysosporium.
The Impact of Drip Irrigation on Heap Hydrology and Microbial Colonies in Bioleaching
Authors: Fagan Marijke A. , Ngoma Emmanuel , Chiume Rebecca A. , Minnaar Sanet H. , Sederman Andrew J. , Johns Michael L. , Harrison Susan T.L.
Published: October 2013

In heap bioleaching iron and/or sulfur oxidising microorganisms are used to facilitate the oxidation of base metal sulfides in ore, thereby liberating the metal ions (e.g. Cu2+) into the leach solution. The heap performance is consequently strongly influenced by the contacting of the leach solution and the ore particles. In this study two setups were used to examine irrigation from a single drip emitter, one of the most common methods of heap irrigation. The distribution of liquid, microbial colonisation and mineral recovery in a bioleach of a 132kg “ore slice” of agglomerated ore were monitored using sample ports positioned along the breadth and height of the box over a period in excess of 500 days. A specialist magnetic resonance imaging (MRI) method which is insensitive to the metal content of the ore was subsequently used to examine the effect of flow rate and particle size distribution on the liquid flow into a smaller bed. Overall the lateral movement of the liquid increased with bed depth, though preferential flow was evident. The majority of the liquid flow was in the region directly below the irrigation point and almost no liquid exchange occurred in the areas of lowest liquid content at the top corners of the samples. This had a significant impact on the local leaching efficiencies and microbial colonisation of the ore. The MRI studies revealed at steady state, the majority (~60%) of the liquid flowed into established large channels. There was minimal exchange with low liquid content regions (presumably stagnant liquid) despite their accounting for more than 16% of the total liquid hold-up. The effect of increasing the flow rate was to retard lateral liquid distribution while slightly increasing the liquid hold‑up in large channels in the region below the irrigation point. Hence poor lateral liquid distribution in drip irrigation was identified as a significant disadvantage of the method.
Impact of Heavy Metals on Denitrification of Simulated Mining Wastewaters
Authors: Zou Gang , Ylinen Anna , Di Capua Francesco , Papirio Stefano , Lakaniemi Aino Maija , Puhakka Jaakko
Published: October 2013

Thespreading of nitrogenous compounds into the environment is a common challenge duringmining industries. Typical explosives used in mining are N-based compoundswhich lead to nitrogen contamination of groundwater and water bodies. In goldextraction, cyanide used as lixiviant is also another source of nitrogen pollution.The present work aims to investigate the effect of heavy metals ondenitrification using batch bioassays. Cu, Ni, Co and Fe influence ondenitrification process was studied at pH 7.0. Below the soluble concentrationof 62 mg/L, Ni did not inhibit denitrification, whereas denitrification wasrepressed at soluble Ni concentration above 62 mg/L. At 122 mg/L of soluble Ni,50% inhibition of denitrification was observed. Below soluble concentration of86 mg/L, Co exerted no inhibitory effect on nitrate removal but moderatelydecreased the denitrification rate. Cu slowed denitrification down resulting in40% of nitrate removal averagely at the soluble concentration below 1 mg/L. Onthe contrary, Fe supplementationresulted in iron oxidation and soluble Fe concentrations ranging from 0.4-1.6mg/L that stimulated denitrification. Thepresent work indicates that denitrification can tolerate heavy metals and canbe suitable for acid mine drainage remediation.
Optimisation of Acid Bioleaching of Metals from Pyrithic Ashes
Authors: Vestola Elina A. , Mäkinen Jarno , Korhonen Tero , Neitola Raisa , Kaksonen Anna H.
Published: October 2013

Solid waste from sulphuric acid production contains high concentrations of metals that are harmful if released to the environment. The purpose of this study was to evaluate the acid bioleaching of metals from a sample of pyritic ashes, consisting mainly of hematite. Bioleaching was tested in shake flasks and continuously stirred tank reactors (CSTR) inoculated with iron and sulphur oxidising acidophiles. Solubilisation of metals was mainly achieved through acid attack due to the formation of sulphuric acid by sulphur oxidising bacteria.
Environmental Impact on Soil, Water and Plants from the Abandoned Pan de Azúcar Mine
Authors: Plaza Cazón Josefina , Benítez Leonardo , Murray Jesica , Kirschbaum Alicia , Kirschbaum Pablo , Donati Edgardo
Published: October 2013

Abstract. Pan de Azúcar abandoned mine is located in Jujuy province, Argentina. The impact of that pollution was evaluated determining the density and the composition of the vegetation around the tailings. Also soil and plants samples were collected and their metal contents were determined. Deyeuxia breviaristata was the main native plant in the most polluted soils and its biomass had the highest concentration of zinc and lead. Acid mine drainage (AMD) samples were collected and their toxic effects were analyzed by ecotoxicology assays employed Lactuca sativa L. seeds; CI50120 of 0.03 % v/v was determined. From mineral and AMD samples some iron- and sulphur-oxidizing microorganisms were isolated and also characterised by molecular techniques. AMD potential was evaluated for different tailing samples inoculating native microorganisms; deeper samples produced drainage with pH close to 1 and released iron above of 1000 ppm. AMD can reach Cincel River which is the main tributary of Laguna Pozuelos (just 25 km from the mine). Laguna Pozuelos is a Natural Monument, Biosphere Reserve and Ramsar site.
Precision Machining and Optimisation of Cutting Conditions
Authors: Madl Jan
Published: October 2013

Precision hard machining is a topic of high interest at present. Surface integrity requirements increase. Precision machining may substitute some abrasive operations with some advantages of precision machining over the abrasive machining. But, the availability of hard machining over abrasive machining can also lead to economic advantages. Manufacturing processes, machine tools, cutting tools, tool changes, cutting conditions, etc., are nowadays usually determined intuitively, very often non-professionally, without careful analysis and economic calculation. The determination of cutting conditions is very important aspect of the total optimisation of manufacturing processes. Hard machining is possible to realise by different cutting materials, especially by cubic boron nitride, ceramics and some types of sintered carbides.
Study of the Effect of the Cutting Force Decomposition on Machined Surface when Hard Turning
Authors: Beňo Jozef , Maňková Ildikó
Published: October 2013

Hard turning is well known as removal process making the most of very small chip cross sections. Because of the tool nose radiustodepth of cut ratio, forces in hard machining gather their effects at tool nose radius to produce parasitic portions in all components of resultant cutting force. In order to identify parasitic forces, chip cross sections have been modeled as projections of the shear planes. Based on measured forces data and roughness' in hard turning with cubic boron nitride inserts , the ratios of parasitic effects on resultant surface roughness have been determined. Specific forces per chip cross section/tool edge result from decomposition of measured data in hard turning. Results showed that there is considerable relationship between parasitic portions in passive forces and resultant surface roughness.
Technological Method for the Finishing Process of Fusible Alloy
Authors: Kulikov Mihail U. , Inozemtsev Vitaliy E. , Oo Myo Naing
Published: October 2013

The way is developed by the combined process of finishing machining. In this method, surface treatment is due to the combined effects of cutting tool and anodic dissolution of metal under the influence of an electric current in the electrolytic solution. Applying of this method allow the processing of aluminum and copper alloys to obtain higher quality parameters of the obtained surface, including special material.
Goodness Indicator and Technological Optimization of Honing
Authors: Szabó Ottó
Published: October 2013

Optimisation of technological processes is an important field of research of machining processes. Honing process, its aim and results are affected more factors. Effectiveness is expressed by the following parameters: accuracy, surface roughness, complex surface quality (integrity),material removal rate, costs and productivity of the process. Developed method helps the technology planning and with the introduced new goodness indicator, investigates and corrects it. Optimization and minimization of costs can be ensured at given technological circumstances and technological parameters. With adjustment of the pressure (p) and the cutting speed (vc) economy of the process can be increased in the factory. Developed method can be applied for machining by other abrasive cutting tools. The paper summarizes new results of this theoretical and experimental research.