Search Documents

Due to problems with old technologies more and more product designers have turned to liquid crystal (LC) displays, which have consequently experienced phenomenal growth. The success of liquid crystal displays has fostered continued development, to the point where full-color video displays have been realized which can rival. The details of the lens structure and of the devices fabrication and performance are described using the Jones matrix method. Director n can change from point to point and is, in general, a function of space.. The transition can be approached by changing the impurity concentration or, indirectly, by tuning the temperature since the pinning strengths of the random and crystal potential have in general a different temperature dependence. Light from the conventional light source or laser is passed through a polarizer and then incident on the specimen. The resist profile simulation is carried out using the combined data thus obtained. The nematic liquid crystal is clear only when a long range order exists, in the whole medium. At the nematic-isotropic, transition temperature, the medium becomes isotropic and looks clear and transparent.

Jan 1, 2006

By S. C. Flood, J. D. Hunt

"The columnar-equiaxed transition (CET) has been studied numerically under unsteady-state conditions using mathematical models that: (i) include a non-equilibrium undercooling at the columnar front;and(ii) describe the simultaneous evolution of the columnar and equiaxed zones.The results are discussed and compared with those produced by a steady-state analysis.IntroductionThe majority of the previous work on the columnar-equiaxed transition (CET) has concentrated on the production of equiaxed nuclei, regarding this as being the critical step in the formation of an equiaxed zone. Recently, the growth of equiaxed grains has been considered and this is not unreasonable because, for an equiaxed zone to be present, the grains must grow as well as nucleate. Since the growth rate of the grains will be determined by the thermal environment at and ahead of the columnar tips, it was decided to model the liberation and flow of heat during solidification to discover whether the various trends in the columnar range might be explained by their effect on the temperature profile throughout the casting. The models presented here for the solidification of a casting are the first to include the latent heat liberated ahead of the columnar front. Burden and Hunt (1) consider its effect only qualitatively, and although Lipton et al (2) adopt a criterion for the CET which is based on the thermal interaction of the columnar and equiaxed grains, they do not actually include the latent heat in their calculations.It can be argued that the latent heat liberated by the equiaxed grains in the bulk will retard the columnar dendrites in a casting: once the equiaxed grains are sufficiently well-established, the latent heat that they evolve could slow down the columnar growth to such an extent that the equi axed would dominate. Alternatively, the latent heat produced by the equiaxed grains might suppress further equiaxed solidification by raising the bulk temperature. The nature of the thermal interaction between columnar and equiaxed growth is not obvious, and because it is dependent on the material parameters and the dimensions of the system, it cannot be considered effectively in a qualitative way but has to be studied quantitatively: hence the need for the mathematical models discussed in the following pages. The results of the models are discussed in the light of a steady state analysis."

Jan 1, 1986

By A. N. Lasseigne

Hydrogen storage capabilities of LaNi5 intermetallic compounds were investigated utilizing the combination of thermoelectric power, Beeghly Ester-Halogen digestion, and Leco hydrogen determination. Thermoelectric power has demonstrated a rapid hydrogen assessment capability and can achieve the equivalent of the pressure-composition-temperature (activity) diagram. Effective use of hydrogen storage materials occurs in the two-phase, alpha+beta region of the PCT diagram. A thorough assessment of the content of each phase in this two-phase region to optimize performance of the hydrogen storage materials is described. Practices using the combination of these three analytical practices for rapid characterization of LaNi5intermetallic alloys are discussed.

Jan 1, 2006

By Bin Xu, Qian Li, Xiaoliang Liu, Yongbin Yang, Hongwei Li, Tao Jiang, Yan Zhang

The direct cyanide leaching rate of gold from a gold calcine was only 71.33%, due to 19.51% of gold being encapsulated in the iron oxides. To enhance the cyanide leaching of gold, the calcine was pretreated with acid or alkali washing. The mechanisms by which acid and alkali pretreatment improve gold leaching from calcine are investigated through chemical analysis, XRD, and SEM-EDS characterization.

Mar 1, 2017

By Alan P. Prosser

The heap leaching of gold ores by cyanide solution was simulated by computer program. The program uses only basic m1neralogical and chemical data; no process testwork data, such as column leach results, are required. The simulation can be used to forecast the consequences of various changes before and during the testwork, design and operation stages of a particular ore-process system. Also, data about the state of different parts of the heap at various times help create an understanding of what is happening. The effects of mineralogical and process variables on the overall performance of the ?heap leaching process are illustrated. Comparisons are made to column leach tests and production data. The potential of the simulation strategy is discussed for making better use of operating experience and for suggesting specific research objectives. It has become clear that more attention should be paid to other metals that dissolve in the solution.

Jan 1, 1989

By S. K. Shaha, A. Gryguc, S. B. Behravesh, B. Williams, M. Wells, H. Jahed

Warm forging to near final product geometry shows promising benefits in terms of microstructure refinement and texture modification. In the present study, Semi-closed die forging was performed on extruded AZ80 magnesium alloy at a forging temperature of 400 °C and various forging ram speeds. Compression tests were performed to investigate the influence of forging at various deformation rates on the performance of extruded AZ80 magnesium alloy. The microstructural analysis showed that the extruded AZ80 possesses a grain structure typical in wrought magnesium alloys, with sharp basal texture. In contrast, the forged samples had a recrystallized microstructures and a spatially varying textures and crystal orientations resulting from the complex flow behaviour within the closed die forging. Furthermore, once forged, a significant increase in the material isotropy, homogeneity as well as failure elongation were observed. An increase in UCS of 9% was observed in the forging direction, while the UCS in the extrusion direction was similar to that before forging. The changes in UCS can be attributed to both the refined grain microstructure and crystal reorientation. Successful microstructure recrystallization occurs for strain rates which traverse several orders of magnitude, and in general, UCS isotropy increases with increasing strain rate. It is believed that forging cause’s grain refinement and texture modification which act to enhance the mechanical performance (UCS, fracture strain and superficial hardness) for the forging conditions investigated in this study.

Mar 1, 2017

By Gaifeng Xue, Lei Zhang, Aimin Duan, J. Y. Hwang, Lina Wang

"The removal of chemical oxygen demand (COD) from coking wastewater was experimentally investigated using a three-dimensional electrode reactor. The experimental results showed that the refractory organics in coking wastewater can be effectively removed by this process, and COD removal efficiency was affected by the operating parameters, such as electrolytic retention time, particle electrode dosage, initial pH, current density, aeration amount and electrical conductivity. The experimental results show that the three-dimensional electrode could have a COD removal efficiency of more than 60% and a running cost of no more than 6 YUAN (RMB)/t. This indicates the great potential of a three-dimensional electrode reactor in engineering applications as an advanced treatment methods for coking wastewater.IntroductionCoking wastewater is generated from coal coking, coal gas purification, and by-product recovery processes of coking; it is composed of phenolic compounds, heterocyclic compounds, polycyclic aromatic hydrocarbons, ammonia, cyanide, polycyclic nitrogen-containing aromatics, acyclic compounds, etc. Most of these constituents are refractory, poorly biodegradabile, toxic and carcinogenic [1-3]. Currently, coking wastewater is usually treated by different forms of A/O biological nitrogen removal processes as the primary treatment means, but the aforementioned processes are not efficient enough to meet the requirements of the National Discharge Standard in China (GB13456-1992). According to the continuous requirement on improving environmental protection for the coking industry (revised 2008), increasing wastewater utilization ratios and reducing the discharge of effluent in the coke industry have to be implemented for cleaner production and sustainable development. Therefore, advanced technologies need to be developed to treat coking wastewater and reutilize the product as industrial cooling water, which would be one of the best choices to achieve zero discharge of wastewater and reduce water consumption per ton of steel produced. In this study, a three-dimensional fluidized bed electrode reactor was adopted for the advanced treatment of coking wastewater, and the effects of operating conditions, including particle dosage, initial pH, current density, supporting electrolyte, as well as aeration amount on the COD removal rate, were investigated. Its running costs were also estimated."

Jan 1, 2012

By Pan Cao

The process of reduction roasting of nickel laterite with rotary hearth furnace combined with magnetic separation becomes a very potential way to prepare ferronickel alloy, especially for the low grade nickel laterite ore. In order to realize this new process, the effect of roasting temperature, time and additive on the reduction degree were investigated in the laboratory experimental. The results indicated that the recovery rate of Ni increased with the roasting temperature increasing to 1500°. Most of nickel and a spot of iron are selectively reduced with adding 25.19% SiO2, 6.42% coal, and roasting for 60min at 1500℃. Then conventional magnetic separation was carried out. The content of Ni and Fe are 7.50% and 59.08% in ferro-nickel nugget prepared by this method. And the recovery rate of Ni is 90.91%, which indicates that a high recovery of ferro-nickel from nickel laterite ore is achieved indeed.

Jan 1, 2014

By R. P. King

The linear intercept distributions provide unambiguous and accurate characterizations of the texture of mineralogical materials. The relation between the measured linear intercept distributions and the spatial correlation function is shown to be given by: in the Laplace Transform domain. The linear intercept distributions of the two phases in a low- grade chromite-serpentinite ore were measured. and the spatial correlation functions for both phases were evaluated using the above relation. The correlation functions are the primary relations for integral geometric models of mineralogical texture and this work demonstrates the relation between the 10 stereological model and the 3D integral geometry model for mineral liberation.

Jan 1, 1991

By Helfried Nafe

"For about a century thermodynamically absurd facts have been propagated in conjunction with the iron-carbon phase diagram. These facts concern fundamental relationships of chemical thermodynamics. Attention is turned here to the discussion of only one of the relevant aspects of the subject, i.e. the definition of the thermodynamic activity of the solute and its implications for the iron-carbon solution.IntroductionThe view on the iron-carbon solution is characterized by the assumption that the solute may appear in two different forms, i.e. graphite and cementite. Accordingly, two carbon solubilities are differentiated, on the one hand for graphite and, on the other hand, for cementite. As a consequence, two versions of the phase diagram exist simultaneously, the application of which depends on the prevailing conditions, (i) the so-called stable phase diagram with graphite as solute and (ii) the metastable one that is based on the cementite-in-iron solution. These diagrams are joined together in the double phase diagram that originates from Heyn [l ], with the first ideas mainly going back to Stansfield [2] and Charpy [3].Thermodynamically, the most inadequate implication of the Fe-C double phase diagram is that the carbon activity may take values larger than unity. With the standard state of the activity being that of the pure substance, i.e. the Raoultian one, such a value implies the nonsensical existence ofa state purer than pure. The explanation of this physical state, ifthere is any, vaguely refers to supersaturation and, in the wider sense, to the physico-chemical phenomenon of metastability. Other aspects of chemical thermodynamics are likewise involved. Therefore, the comprehensive investigation into the present subject requires more topics to be considered than only one separate issue. Not only should the criticism of the present view be in the focus but also the discussion of new ideas capable of reconciling the experimental facts, known about the F e-C system, with the fundaments of chemical thermodynamics. All this, however, cannot be provided here because of the limited space available. As a consequence, in what follows only a part of the whole problem is under scrutiny, i.e. the definition of the thermodynamic activity and its role for the interpretation ofrelevant experimental facts."

Jan 1, 2014

By S. V. Cherty

The utilization of natural gas in non-ferrous industries during smelting and refining stages of copper , aluminum, zinc and lead was studied. The total amount of nonelectrical energy consumed in the production of zinc, copper, lead and aluminium, are 96.5% ,93%,92%, and 6 % respectively. It is calculated that 9.45 wt %of air of stoichiometric amount can be substituted by natural gas to the total air input in the nonelectrical energy utilization processes. The results showed that the non electrical energy may be substituted to an amount of 71 % ,52 % ,35 % ,32 % ,and 26% ,in the production of lead, aluminium (plates, foils) copper, aluminium, zinc, respectivelly. Similar calculations are carried out in terms of energy in Btu for the total production of non-ferrous metals in the U.S. It shows that 51.866~106 millions of Btu of nonelectrical energy can be substituted by 54.58~106 cu. ft of natural gas. Finally, the substitution of non electrical energy in terms of equivalent coal energy is discussed. 1t is shown that total non electrical energy is equal to 1.852 million tones of coal .If this 1.852 million tones of coal is replaced by natural gas, a total savings of 22.14 million dollars are achieved. The total or partial substitution of coal by the natural gas in the existing industrial processes and modification of redesigning the processes is discussed.

Jan 1, 1993

By Wankun Wang, Fuchun Wang

Based on the study of artificial neural network, the neural model was established for the prediction of germanium extraction from zinc oxide dust by microwave alkaline roasting-water leaching. Alkali-material mass ratio, microwave heating temperature, liquid-solid ratio, aging time, leaching time and leaching temperature were the significant factors for the process. The results indicated that the neural network prediction model was reliable, and the forecast values fitted well with the actual experimental values. The model could be used to predict the regeneration experiments with high credibility and practical significance. The accuracy of convergence of the model reached 10−5.

Mar 1, 2018

Over the years, numerous hydrometallurgical processes have been proposed as an alternative or complement to smelters for the treatment of copper concentrates. Most of these initiatives met with limited success. Bioleaching is applied commercially for secondary copper minerals heaps and dumps, and bacterial leaching processes are being developed for copper concentrates, although industrial application is still years away. More recently developed processes usually include pressure leaching and/or ultrafine grinding. This paper proposes a new leach process to treat copper sulphide ores or concentrates: the process operates under atmospheric pressure and uses limited concentrations of ferric sulphate as oxidant; the key to the process is the regeneration of the ferric ion, which can be effected in-situ (direct process) or ex-situ (indirect process) using SO2/O2. Examples are presented for the treatment of copper concentrates by agitation leach and of copper ores by heap leaching. Application of the process to copper gold ores and chalcopyrite concentrates is also discussed.

Jan 1, 1999

By B. C. F1intoff, R. G. Bradburn, E. Groiss

"The concentrator at Brenda Mines Ltd. treats a copper - molybdenum porphyry ore with current head grades of 0.185% Cu and 0.036% Mo. The consistently low head grades provided the driving force to explore methods of improving plant productivity. Computer based process control was recognized as one means of addressing this objective. Over the period from 1974 to 1982 a control system evolved which now extends to every area of the mill. Control strategies are built on elements of classical, modern and rudimentary expert control. In addition, the control system has often served as a catalyst for other technological developments. The economic returns associated with the system are very significant and it has played an important role in the mine's survival in times of poor metal markets. This paper presents an overview of the computer control system at Brenda.PreambleOne can scarcely avoid picking up a trade magazine or newspaper today without seeing some reference to technology and its potential impact on North American business. _A recurring theme is the need to apply technology to raise our standard of plant automation in the manufacturing and process industries. The general thesis of these articles has been concisely captured in the mutually exclusive set:AUTOMATE or EMIGRATE or EVAPORATEProcess control is one form of automation that has been successfully exploited by various sectors of these industries. In minerals and metal processing the wide scale adoption of process control technology has, until recently, been largely limited to a few companies - most of whom have a history in the area dating back to the early 1970’s. However, there is definitely an increased and much broader interest in process control as a technology which can improve performance, productivity and profit.The economic hardships that were visited on the mining industry in the early 1980's are not easily forgotten. It is the authors' conviction that the mining industry must move to implement proven technology, in particular process control, in order to be well postured for the next (inevitable) down cycle.In pursuing the technical and trade literature, one can discover a number of example of the successful utilization of process control systems in mining and related applications. In the text which follows, the authors describe the process control efforts undertaken in the Brenda Mines Ltd. concentrator."

Jan 1, 1989

By Batric Pesic

Dissolution of gold with sodium bromate solutions of various compositions was studied by using a rotating disc technique. The role of bromide ion, acid and externally added bromine was examined. It was found that sodium bromate could not dissolve gold in the absence of either acid or bromide ion, or both. When acid was absent, no bromine necessary for gold dissolution could be produced. When bromide ion was absent, formation of soluble gold bromide species, AuBr,-, was not possible. Bromate concentration had a complex effect, and it was dependant on bromide ion concentration. For fixed initial bromide ion concentration, gold dissolution rate increased with sodium bramate concentration increase until certain level, beyond which further increase of bromate concentration decreased the gold dissolution rate. The negative effect of bromate was explained by the depletion of necessary bromide ion. Sulfuric acid concentration effect was a function of initially present bromine.

Jan 1, 1992

By Florian Kongoli

While calcium ferrite slags have been successfully used in continuous copper converting for the last 30 years, ferrous calcium silicate slag was proposed about 8 years ago as an additional alternative for copper smelting. Although both slags are normal extensions of each other their phase relations have not been completely clarified. In this paper the liquidus relations of both slags have been quantified at various areas that cover both of them. The existing experimental data have been first reviewed and discussed in relation to the solidification procedure. An original physical model is then used to predict various diagrams of the liquidus surface of both slags. It is shown that the ternary liquidus diagrams normally used for FeOx-SiO2-CaO system are not suitable for industrial slags. The new model diagrams of Fe/CaO versus SiO2 and Fe/SiO2 versus CaO as well as Fe/CaO versus Temperature and Fe/SiO2 versus temperature are proven to be much more convenient for ferrite and ferrous calcium silicate slags. Based on these diagrams the effect of SiO2 and CaO on the melting temperature is quantified. The effect of Cu2O is also quantified through the model. Some Fe/CaO versus Cu2O and Fe/SiO2versus CaO at various copper contents are predicted and the results show good agreement with the experimental data. It is also shown that in the presence of liquid copper, Cu2O is dissolved in the slag depending on the oxidation degree of the system and might lower the liquidus temperature. Some discussions are also presented taking into account plant observations and important conclusions are drawn for copper smelting and converting

Jan 1, 2006

By Chen-Ming Kuo, Esher Hsu

"Under the 4-in-1 recycling system, Taiwan producers and importers who using packaging containers have responsibility to pay the recycling fees for recycling the waste packaging containers they produced or imported; while the collectors/recycling plants who collect/sort/recover waste packaging containers receive subsidy for conducting recycling. A reasonable pricing for recycling charge and subsidy is a way for sustainability of the recycling. The objective of this study is to provide an amending mechanism for product charge and recycling subsidy in response to the social economic changes. This study employs a regression analysis and cost adjusting model to link the factors used for calculating product charge and recycling subsidy on recycling waste packaging containers with socio-economic indicators, raw material prices, wholesale prices, and secondary material prices. Study results provide estimated models to EPA in Taiwan for amending product charge and recycling subsidy in response to the social economic changes.IntroductionUnder ""4-in-1"" recycling system in Taiwan, waste packaging containers are officially announced to be recycled. The waste packaging containers announced to be recycled include iron cans, aluminum cans, glass bottles, plastic containers, paper containers, aluminum foiled paper packs. In order to compensate the recycling system, EPA charges associated manufacturers and importers for recycling fee and subsidies recyclers to create the economic incentive for raising recycling performance. Basically, the budget for subsidy recyclers is from the recycling charge. That means if we want to increase recycling efficiency by increasing subsidy to recyclers then the manufacturers and importers have to pay more for reaching financial balance of recycling foundation. The benefit of recyclers and fee payers are always conflicted. The recycling charge and subsidy is thus argued by fee payers and subsidy receivers all the time. A reasonable pricing for recycling charge and subsidy is the only way to keep the recycling system sustainable. Moreover, a suitable mechanism has to be changed along with the changing social economic condition. The recycling performances and effectiveness of this recycling system is also highly dependent on the pricing mechanism. This study intends to provide an amending mechanism for product charge and recycling subsidy in response to the social economic change. Related previous studies about recycling system in Taiwan with its performance include Hsu and Kuo (2002, 2005), Bor, Chien, and Hsu (2004) and Hsu (1999). Hsu and Kuo [1] estimated total production values of recycling and evaluated the performance of recycling performance based upon the estimated production values."

Jan 1, 2011

Today’s world relies upon advanced green technologies that are made of critical elements with unique properties. Examples include rare earth elements (REEs) that are critical in the manufacturing of wind turbines and electric/hybrid vehicle batteries, key components of a greener future that face supply uncertainty and near zero recycling. To tackle their supply challenges, activities have begun for urban mining from waste electrical and electronic equipment (WEEE) that contain considerable amount of REEs, but their current level of recycling is less than 1%. Current recycling practices use either pyrometallurgy, which is energy intensive, or hydrometallurgy that utilizes large volumes of acids and solvents and generates large volumes of hazardous waste. In this study, we developed a novel and sustainable process to recycle REEs from WEEE, NiMH batteries in particular. The developed process relies on supercritical fluid extraction (SCFE) utilizing CO2 as the solvent, which is abundant, safe, cost effective, and inert. The effect of seven operating parameters, namely temperature, pressure, residence time, sample to chelating agent ratio, agitation rate, complex formulation, and methanol addition on REE extraction efficiency was investigated, and optimum operating conditions were determined. This work is the first to utilize a very efficient and safe process that runs at low temperature to extract metals from postconsumer products with minimum hazardous waste generation, while offering about 90% leaching efficiency for REEs. We expect our process to find widespread applicability in urban mining of REEs using green chemistry.

By Henrique Kahn

The Anitapolis alkaline massif in southern Brazil underlies a sub circular area of 6 km2. Bore-hole data show a concentric rock distribution, with mafic rocks in the central part and felsic rocks in the border zone. The rocks are covered by talus and weathered material, 30 m thick on average, and very inhomogeneous in composition. Phosphate mineralization associated mainly with two levels of the weathering mantle and with fresh rocks. A preliminary ore-type classification was based on distribution of apatite, feldspar, vermiculite, biotite-phiogopite, calcite, pyroxene, amphibole and analcime, determined by semiquantitative diffraction method. Technological tests performed on eluvial ore samples from three adits resulted in a subdivision of ore-types based on the difference in behavior due to mineral characteristics during mineral pr

Jan 1, 1991

By S. L. I. Chan, M. Z. Quadir, D. C. Austin, P. J. Hazell, A. Chen, A. A. H. Ameri, D. East, J. P. Escobedo, M. A. Bevan, A. D. Brown

The microstructure and mechanical response of additive manufactured Ti64 under compression and tension has been investigated. Quasi-static and dynamic experiments were conducted on electron beam powder bed Arcam A1 (EBM) and blown powder laser Optomec LENS MR-7 (LMD) additive manufactured specimens. Hot isostatic pressing (HIP) was conducted on both of the additive manufactured specimens and results were compared with as-received specimens. Digital image correlation (DIC) was utilized to observe the in situ development of deformation fields during tensile loading. Optical microscopy was conducted on pristine and deformed specimens to examine the microstructure of the specimens. HIP treatment reduced the porosity by *90% with a concomitant increase in hardness by 40%. The results from tensile experiments show that additive manufactured Ti64 display a higher values for the yield stress, hardness, and ultimate tensile strength than conventionally manufactured Ti64. Under quasi-static compression, it was observed that EBM specimens exhibit a higher yield strength and ultimate tensile strength than LMD specimens.

Mar 1, 2017