AMIRKABIR
Year:2009 | Volume:20 | Issue:20-C|Papers Count:14

A technical solution for the still existing problem of curing high strength concrete is proposed. The new method uses a blend of aggregates containing lightweight aggregates. The prewetted grains become a water supply at the disposal of the hardening and drying cement paste, allowing a continuous hydration which leads to improved properties of the concrete.

Cementation is one of the processes employed for recovering Copper from leach liquors especially in small scale mines. The kinetics of cementation is important because of its effect on the capital and operating costs. In this research, the effect of agitation intensity, Cu-concentration, pH, iron surface and reaction time on the cementation kinetics of copper from Cheezeh ore leach liquors has been investigated. The experimental design method was carried out by using the 2k factorial approach. Experimental results showed that agitation intensity, Cu-concentration, pH and interaction between Cu-concentration and Ph have the most significant effect on cementation kinetics. Optimum conditions were agitation intensity = 300 rpm, pH=L Cu-concentration= 7 g/l and iron surface= 31.2 cm2. The kinetic constant under these conditions was estimated as 7.66*10-3min-I.

So far, Estimation of the number of reserved stopes in underground mining has only been carried out based on empirical methods. Not any accurate criteria have normally been employed in these methods. Thus, the confidence level for substituting the reserved stopes instead of failed stopes, so that the mine production is continued, is not predictable.In this paper, a new method is presented to compute the confidence level for continuation of mine production. This method is based on the assumptions of knowing the number of the main stopes, the probability of the failure of the active stopes and the probability of repairing the failed stopes. In this method, the main and the reserved stopes are modeled, and then applying the Markov chains, the probability of using the reserved stopes during the mine production period is estimated.

Kervian mining area is the first area for genesis of shear zone-related gold minenilization in Iran. The aim of this study is completion of structural geology aspect, analysis of 3D model and finally the determination of structural controls in mineralization. Based on the structural evidence, three episode of deformation were recognized in the Kervian shear zone. Between this stages, Second stage(D2) have been caused development of Milonitic foliation and the most intense of structural deformation in study area. The dip and strike of faults was determined based on Stereoprojection and Roze diagram. These faults were classified in two goups. First group, are thrust faults that have NE-SW strike and 40-60° dips to NW. Second groups of faults, are vertical faults that indicate strike-slip right lateral motions. Then, 3D model of Kervian deposit were drawn with Datamine software. A comparison of structural evidence to 3D modeling indicate that mineralization current at depths of 125-200(m) and perfectly isoclinal with geology structures in Kervian. These evidences indicate that main factor of mineralization is controlled by structural factor's in Kervian mining area.

In this paper transport tests are carried out on concrete and mortars of gradually increasing Aggregate Fractions (AF) to examine the validity of ITZ percolation theory that blames the sudden increase in porosity of the mortar at a critical aggregate fraction on the joining up of the ITZs together to make a continuous path way through concrete. Test Results and their effects of the validity of the percolation theory are discussed. It is suggested that the jump in porosity at the critical aggregate fraction may be completely independent of ITZ altogether and two candidates of aggregate spacing and paste roughness have been proposed to replace ITZ percolation as the cause of this sudden increase at the critical aggregate fraction. The need for further tests have been established to elucidate the remaining ambiguities as to what exactly happens to the paste in concrete and its porosity as the volume of the aggregate is increased to and beyond critical value.

There are several methods that may be applied to separate geochemical anomalies from background, each of them has advantages and disadvantages. In this paper, concentration-area model and orthonormal trend surface method are used to separate geochemical anomalies from background for the stream sediment samples in Sorian, which is located in the northern part of Fars province. The principal of the second method is the fitting of a polynomial function of geographic location to the measured geochemical data. This polynomial is considered as a regional effect representing background component of the measured data. The residual component is obtained by subtracting the regional component from the observed geochemical values. Several residual anomaly maps with different trend orders were plotted and the best trend was selected to determine anomaly zones for each element. The results of two methods are close in determining the anomaly zones for each element.

One of the most important characteristics in the reservoir studies known as "determination of porosity and permeability". Porosity and permeability determination is done by different methods such as experiment on small samples in laboratory or insitu determination using well logs. The difference between these methods is due to scale effect as changing in sample volume has different results. In this paper, the scale effect on porosity and permeability variables from an oil reservoir using geostatistical approaches (basically variance of mean) are considered. The results of autocorrelation function show that the lateral permeability increases with scale. This is different for vertical permeability, which decreases with increasing the sample scale.Study of the variorum function shows that the reservoir is anisotropic. The results obtained by variance of mean approve this conclusion. So, variance of mean can be used for studying the anisotropic behavior.

In this work, extraction of Fe (II) by bis-2-ethylhexyl phosphoric acid (D2EHPA) and effect of arameters such as pH, temperature, concentration of D2EHPA and TBP are investigated. Based on the experimental results, iron is extracted in higher pH, using equal to or less than 20% Vol D2EHPA in sulfate media. While, using more than 20% Vol D2EHPA in chloride media, iron is extracted in lower pH. Moreover, iron extraction curves shifte to the left by increasing of D2EHPA concentration. In addition, increasing of the temperature, in chloride media, leaves the iron extraction curves without any change and brings about shift to the left when iron is extracted in sulfate media. In addition, extraction of iron is exothermic in both media. Furthermore, increasing of TBP up to 1OV01%lead iron extraction curves shift to the right about 0.2-0.3 of pH unit. Therefore, iron may be extracted at high pH ranges if conditions such as 20% Vol D2EHPA or less plus 5-10% Vol TBP in media sulfate are chosen. Consequently, iron can be stripped easier, using low concentrated acid.

Platinum-Group elements (PGE) deposits often found with layered mafic-ultramafic association and PGE enrichments occur in Cu and Ni-rich sulfide mineralization. It has been shown that elements ratio, as well as chondrite-normalized metal patterns can be successfully used for evaluation of PGE enrichment. Faryab ophiolite area is the main resources of chromite in south of Iran that has sulfide mineralization in different lithology. Sulfide phases recognized by Microscopic methods. It indicates that main sulfides are include pyrrhotite, pentlandite, millerite and heazlewoodite. Samples (18 Samples) are analyzed by ICPMS and Results indicate that partial melting has occurred and PGE mineralization has done. Determination of accurate content of PGE in other rocks required more studies.

Main goal in this article is presenting a new method to separate the vary lithologies from granite and granodioritic rocks, applying Remote Sensing (RS) and Geographic Information Systems (GIS), with the least error within a local geological area of Shirkooh-e-Yazd. All the analyses are based on the Landsat satellite image of the studied area. To do so, the chosen formatted images is converted into the RS and GIS formats. Applying the local image bands composition, a seven band color image has been presented. Fusing the color imaged into the pan bands ones, a new image has been produced with the segregating distance ability of 15 meters. The image geometry has been corrected by the local point's measurements of GPS in a very accurate position. Different band created colored image was able to separate the lithology within the studied area precisely. The separated lithology of granite and granodiorite were also tested by both supervised and unsupervised classification method. The unsupervised classification was applied in 6, 8, 10 different bands to find the best separation resolution. Also supervised classification has been applied by choosing some areas as controlled locations, where also have been located by GPS. Comparing the different results merged from different methods, e.g. classification and interpretation ones, illustrate the possible important errors in the extracted results. In the last step, a very precise map based on the igneous lithology has been presented.

Semi-Autogenous/Autogenous (SAG/AG) mills are used widely in iron, copper, gold and other minerals grinding. In recent decades, several mathematical models were presented by various mineral processing researchers for predicting the performance of these mills. Computer simulation using these models is one of the validated techniques for predicting of mills power draw. In this work power draw of SAG mills was simulated which is also applicable for predicting the power draw in other types of tumbling mills such as ball mills. This model is based on describing of charge motion and the position of toe and shoulder of charge in the mill and charge kinetics and potential energy. This simulator computes toe and shoulder angles of charge, power requirement for tumbling charge, no-load power, net power and total power of SAG mills.

Rolling process is one of the most important way of metal forming. The results of this process are almost finished product, therefore controlling the parameters effecting this process is very important in order to have cold rolling products with high quality. Among the related parameters, the pressure distribution or friction hill within the roll gap is known as the most significant one.In this study using in new software (MATROLL), after rolling calculation, this process is optimize for producing cold rolled sheets. This software is able to plot the friction hills as well as calculating abut 30 rolling parameters. To verify the software operation, the real industrial rolling was carried out on tow coils of hot rolled products of Aluminum. The obtained results are in good agreements with the findings other researchers.

Magnesium aluminate spinel (MgAI2O4) is a well-known mineral usually used as a refractory material. Indeed, its high melting temperature (2135°C), good chemical inertness, high mechanical strengths both at room temperature and at elevated temperatures, as well as its high resistance to radiation give this material very attractive properties and applications. Nanocrystalline MgAL2O4 spinel powder synthesized using metal nitrates and a polymer matrix precursor composed of egg white. The precursor and the calcined powders were characterized by simultaneous thermal analysis, X-ray diffraction, scanning electron microscopy. According to X-ray results, the inceptive formation temperature of spinel via this technique was between 800°C and 900°C. The calcined powder at 900°C for 2h has spherical morphology with particle sizes about 60nm.

In this research, mechano-chemical synthesis of CO3W/Cu composite nanoparticles on CO3W based intermetallic compound was investigated. Powder mixture of CO3O4, WC and CuO (99/9 % purity) were first milled by high energy planetary ball mill and decline in hydrogen reduction system. During ball mill, powder mixtures at 200rpm, ball to powder ratio (BPR) 15 and time 1 to 4 hours. Synthesis of composite Nano powders on CO3W based intermetallic compound with mean particle size of 30 nm occurred during reduction process at 850-1100°C in tube furnace for 1 hour.