Diagnostic Accuracy of Sixty Four Multi-Slice CT Angiography in Assessment of Arterial Cut-Off and Run-Off in Comparison with Surgical Findings

Background/Objective: The accurate anatomic mapping and determination of the severity of arterial disease, an important health problem of the elderly, is of great significance. We aimed to determine the diagnostic value of 64-multislice CT angiography (MSCTA) in run-off and cut-off sites of arterial disease. Patients and Methods: Throughout the study, MSCTA followed by an operative intervention was carried out on a total of 38 patients with clinical signs and symptoms suggestive of arterial disease (AD) all of whom had the indication for vascular surgery. The mean age of patients was 34±15.86 (range, 23 to 93) years. MSCTA was executed using a 64-slice CT scanner, during the arterial phase of injecting the nonionic, contrast medium with a power injector at the rate of 5 ml/sec into the antecubital vein and exploration and revascularization of peripheral arterial disease was performed intraoperatively. Results: Atherosclerosis and arterial disease, the most common causes of vascular occlusion, were more common in the lower extremities. According to MSCTA findings, the most frequent site of stenosis was the superficial femoral artery. Spearman’s correlation coefficient showed a high degree of agreement amongst the raters. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and the accuracy of MSCTA compared to surgery were 83.8%, 96%, 96.8%, 81.3% and 89%, respectively. MSCTA findings were compared with surgery as a standard of reference, which showed concordance in the majority of cases (81.6%). Cut-off sites were correctly identified by MSCTA in 97.3% of the patients and the most common sites of discordance were the run-off sites (18.2%). Conclusion: MSCTA angiography as a novel diagnostic modality may be a suitable alternative and a viable choice for routine clinical diagnosis

Nanobubbles effect on the mechanical flotation of phosphate ore fine particles

Froth flotation is one of the main methods for processing of phosphate ores. However, flotation of fine particles, especially phosphate ores, has always been one of the fundamental problems. For example, about 10% of Esfordi phosphate processing plant ore with a grade of more than 16% P2O5 and d80 of less than 30 μm is sent to the tailing dam. Flotation using nanobubbles generated by hydrodynamic cavitation is one of the latest industrial techniques to recycle fine particles of minerals. A significant recovery increment in flotation of fine particles using nanobubbles has been one of the main topics of flotation science in recent years. Fine bubbles have important effects on the gas holdup, which is necessary in the froth flotation cell of mineral based process industries. At a given gas holdup, using finer bubbles can reduce frother consumption. An exclusive nanobubble generation system has been developed at Iran Mineral Processing Research Center (IMPRC) for evaluating the effect of nanobubbles on froth flotation. This device enhances venturi tubes and works based on cavitation phenomena. In this study, a comparison of conventional flotation and nanobubble enhanced flotation in mechanical cells was carried out on two types of phosphate ore samples. As a result, the flotation recovery had a significant increment of more than 30% in the case of using nanobubbles versus conventional flotation in the same grade of P2O5

The effect of different parameters on the power draw of miduk copper concentrator sag mill

The aim of this paper was to investigate on the effect of different parameters such as rotational speed, hold-up and load solid percent on the power draw of Miduk SAG mill. Miduk copper concentrator is located in Kerman Province, Iran, and its size reduction stage includes one gyratory crusher which feeds one SAG mill (9.75 dia.(m) * 3.88 length(m)) following two parallel ball mills (5 dia.(m) × 7 lenght(m)). After SAG mill, a trommel screen produces two over and under size materials which the oversize part is circulated into SAG mill and undersize reports to hydrocyclone for further process. An experimental design was implemented in this work using d × 7 software for the above three mentioned parameters. As there is of course some effective factors which are significant on the mills performance such as feed hardness (grindability), liners conditions, but due to the existing variation in feed distribution and grind ability of feed, this decision was made to work on these two factors and accordingly the sampling and necessary analysis were performed. Due to similar technical reasons, it was not possible to change the ball load in SAG mill, as well. The results obtained from this work showed that optimized conditions for mill speed, hold-up and solid percent would be %68.05 of critical speed, 80 ton and %75, respectively

Response surface methodology (RSM) for optimization of chalcopyrite concentrate leaching with silver-coated pyrite

This study aims to leach copper from chalcopyrite and optimizing the leaching process, using the response surface methodology (RSM). The RSM, a D-optimal design with four factors in three levels was employed to evaluate the effect of particle size, temperature, silver-coated pyrite to chalcopyrite ratio and redox potential parameters on the copper extraction efficiency. A quadratic model was then proposed by the RSM to correlate leaching variables. The tests results indicated that the model was significant with the experimental data at a correlation coefficient (R2) of 0.96. The most important parameters of copper extraction efficiency were particle size and silver-coated pyrite-to-chalcopyrite ratio, and also the squared term of particle size (A2), temperature (B2) and redox potential (D2). In addition, the interaction between redox potential and silver-coated pyrite-to-chalcopyrite ratio (CD) was significant. It was shown that the finer the particle size the faster the leaching rate of copper. It was also indicated that by increasing silver-coated pyrite to chalcopyrite ratio of 6:1 copper recovery increased. The maximum recovery of copper (71%) was obtained for the particle size of -38 μm, 70 °C, 420 mV of redox potential, silver-coated pyrite-to-chalcopyrite ratio of 6 and leaching time of 8 hours

The role of ore properties in thickening process

The role of ore properties (density, particle size, and mineralogy) in thickening process was studied in this research. The shaking table was used to prepare the sample for the tests. The tailings were continuously fed on the table by gravity to separate the tailings in three products as slime, middling and coarse particles. The solid density and particle size of the samples were different. To study the effect of mineralogical properties, the sedimentation behavior of the feed and middling samples were tested. The results showed that the free settling velocity of the feed (2–6 mm/s) was less than that of the middling sample (18–23 mm/s), and the compressibility of middling (density: 0.63–0.86 Mg/m3) was more than that of feed (density: 0.33–0.47 Mg/m3). This was due to the amount of clay reduction in the middling sample. The sedimentation behavior of the slime and the coarse samples were also compared in order to study the effect of particle size and density. The settling velocity of the slime and the coarse particles was obtained as 0.1-0.4 and 26 mm/s, respectively, and the maximum underflow density were obtained as 0.35 and 1.57 Mg/m3, respectively. Therefore, the particle size and density reduction reduced the thickener performance. In order to study the effect of particle size, the sedimentation behavior of the slime and coarse samples were compared, and it was obtained that the settling velocity and underflow density increased with the increasing in the particle size

ESTIMATION OF GAS HOLDUP AND INPUT POWER IN FROTH FLOTATION USING ARTIFICIAL NEURAL NETWORK

Multivariable regression and artificial neural network procedures were used to modeling of the input power and gas holdup of flotation. The stepwise nonlinear equations have shown greater accuracy than linear ones where they can predict input power, and gas holdup with the correlation coefficients of 0.79 thereby 0.51 in the linear, and R2=0.88 versus 0.52 in the non linear, respectively. For increasing accuracy of predictions, Feed-forward artificial neural network (FANN) was applied. FANNs with 2-2-5-5, and 2-2-3-2-2 arrangements, were capable to estimating of the input power and gas holdup, respectively. They were achieved quite satisfactory correlations of 0.96 in testing stage for input power prediction, and 0.64 for gas holdup predictio

Recovery of coal particles from a tailing dam for environmental protection and economical beneficiations

Abstract Considerable amounts of coal particles are accumulated in the tailing dams of washing plants which can make serious environmental problems. Recovery of these particles from tailings has economically and environmentally several advantages. Maintaining natural resources and reducing discharges to the dams are the most important ones. This study was examined the possibility to recover coal particles from a tailing dam with 56.29% ash content by using series of processing techniques. For this purpose, gravity separation (jig, shaking table and spiral) and flotation tests were conducted to upgrade products. Based the optimum value of these processing methods, a flowsheet was designed to increase the rate of recovery for a wide range of coal particles. Results indicated that the designed circuit can recover over 90% of value coal particles and reduce ash content of product to less than 14%. These results can potentially be used for designing an industrial operation as a recycling plant and an appropriate instance for other areas to reduce the environmental issues of coal tailing dams

Double reverse flotation of a very low grade sedimentary phosphate rock rich in carbonate and silicate

In this study, reverse flotation was applied to recover phosphate from a very low grade (5.01% of PO) sedimentary ore. Sodium silicate, starch, tannic acid, aluminum sulfate, (Na,K)Tartarat, sodium tripolyphosphate, HPO, and HSO were used as phosphate mineral depressants in acidic and alkaline conditions. Oleic acid and Armac-T were added as carbonate and silicate collectors respectively, while pine oil was used as a frother and fuel oil as modifier. It was demonstrated that aluminum sulfate and (Na,K) Tartarat work synergistically to depress phosphate minerals. An experimental protocol was devised to optimize the grade and recovery of phosphate using two different methods: anionic-cationic and cationic-anionic. Anionic-cationic method was found more effective