International Journal of Engineering
Volume:16 Issue: 1, Apr 2003

Four identical 37.5 Liter UASB reactors R1, R2, R3 and R4 were used to study the effect of sulfate concentration on granule formation. Diluted molasses with COD range 1000–1300 mg/l were used as feed and acclimated cow manure was used as seed. Concentration of sulfate ions in the four reactors were 100, 500, 1000 and 1500mg/l. Granules were observed in R2 after 33 days from startup time, while in R1 and R3 granules appeared after 45 days. No granules were formed in R4. Sulfate reduction efficiencies were 84, 89, 71.5 and 59.4% while corresponding COD removal efficiencies were 85, 91, 84 and 77% for reactor R1 to R4 respectively. Temperature kept at 30ºC allex periments and the best pH for granulation was found to be 7.00.

A synthetic wastewater with high concentration of sulfate and COD was treated in anaerobic baffled reactor (ABR) coupled with an activated sludge. The work was accomplished in two phases. In the first phase, the concentration of sulfate was kept constant at 500mg/l, but COD concentration was increased from (3000mg/l to 6000mg/l), consequently, COD and sulfate removal in ABR reached to 80% and 95%, respectively. Some of produced sulfide in ABR converted to sulfur by photosynthetic bacteria which appeared on the top of the ABR. Effluent from the ABR entered to activated sludge where COD removal reached 60%, but some of sulfide converted to sulfate. In the second phase, at constant concentration of COD, when sulfate concentration was increased from 500mg/l to 1750mg/l by steps about 250mg/l, inhibition was not observed. When effluent of thissecond phase was entered in activated sludge, COD removal was decreased, and sulfide cause bulking in activated sludge. The ABR and activated sludge were worked with hydraulic retention time (HRT) about 24 hours and 15 hours, respectively. The temperature of ABR system was maintained at 35ºC

This paper describes an alternative finite element model that would yield more accurate results in the prediction of the behavior of Profiled Steel Sheet Dry Board (PSSDB) folded plate structures, which can be considered as an improvement of an earlier proposed model. The PSSDB folded plate structures are being proposed as an alternative to traditional forms of roof construction.The PSSDB system is an innovative composite structural system initially envisaged by Wright and Evans. It consists of profiled steel sheeting connected to dry board by simple self-drilling and self-tapping screws. The folded plate roof model under study incorporates individual PSSDB panel assembled and connected to each other by ridge connection plates. Full-scale model of 6-meter span was tested in the laboratory to confirm theoretical models proposed by the authors. The earlier reported model was based on an orthotropic idealization of the profiled steel sheet, and two directional ‘dummy’ plate element in modeling the connection between profiled steel sheet and dry board; a model that has been concluded to be giving good and reasonably accurate results. However,the accuracy of the predicted results could be improved by modeling the profiled steel sheet as an isotropic plate element, and utilizing ‘joint’ element instead of the ‘dummy’ plate element to modelthe connections involved in the PSDDB folded plate structures. This is the focus of this paper. Results found from the newly proposed model generally over-estimated the experimental results, and arewithin 34% of the experimental model.

(Transparent SnO2 thin films were deposited on porcelain substrates using a chemical vapor deposition technique based on the hydrolysis of SnCl4 at elevated temperatures. A reduced pressure self-contained evaporation chamber was designed for the process where the pyrolysis of SnCl4 at the presence of water vapor was carried out. Resistive gas sensors were fabricated by providing ohmic contacts on the layers obtained and the installation of a custom made micro-heaterbeneath the substrate. The sensitivity (S = Ra/Rg) of the fabricated sensors to acetone vapor contamination was measured at 270ºC. S increased linearly with contamination level up to 8000PPM, and saturation was observed at higher concentrations. The experimental relationship between S and thickness of the sensitive film was investigated in films obtained by CVD for the first time. It was shown that S was inversely related to the film thickness, and higher S values were recorded for thinner sensors. The upper limit for S was imposed by the conduction instabilities observed in the thinnest films deposited.

Energy technique procedure for computing the leakage reactance in transformers is presented. This method is very efficient compared with the use of flux element and image technique and is also remarkably accurate. Examples of calculated leakage inductances and the short circuit impedance are given for illustration. For validation, the results are compared with the results obtained using practical tests for 3 types of a small single-phase transformer, 3-phase distribution transformers and a high voltage test transformer were studied.

The performance of a product is often evaluated by several quality characteristics. ptimizing the manufacturing process with respect to only one quality characteristic will not always lead to the optimum values for other characteristics. Hence, it would be desirable to improve the overall quality of a product by improving quality characteristics, which are considered to be important. The problem consists of optimizing several responses using multiple objective decision making (MODM) approach and design of experiments (DOE). A case study will be discussed to show the application of the proposed method.

One of the well-known evolutionary algorithms inspired by biological evolution is genetic algorithm (GA) that is employed as a robust and global optimization tool to search for the best or near-optimal solution with the search space. In this paper, this algorithm is used to solve unequalsized machines (or intra-cell) layout problems considering pick-up and drop-off (input/output) points. Such problems may be formulated as a continuous plane model that is applicable to cellular manufacturing systems. The aim is to assign all the machines to the related locations within the floor plan in such a way that an objective function, as the total material handling is optimized while satisfying all the constraints. In this paper, a GA methodology is used to generate promising and feasible layout solutions and to find the best or near-optimal solution searched within the space problem. For this purpose, a new genetic presentation and genetic operators are designed. Finally, computational results reported by the GA program and a construction algorithm are presented in the context of the test problems. In addition to the above objective function, the dead space ratio of final layout solution is calculated for each test problem.

Iran’s Sarcheshmeh copper industries with an annual production of 120,000 tones are the biggest of it’s kind in South Asia. The main method of production is pyrometallurgical matte making in two reverberatory furnaces which use direct–bond magnesite-chromite refractories supplied by German and Austrian companies. Following a recent major overhaul, bricks in contact with slag, matte and furnace atmosphere were collected and used for evaluation of the hot corrosion mechanisms of MgO-Cr2O3 refractories using OM, Chemical–Analysis, XRD, SEM, EDS techniques. Furthermore, Iranian produced refractories were assessed in the light of the present results for the possibility of replacement. A substitutional diffusion mechanism based on replacement of Fe S and Si compounds with MgO-Cr2O3 and is proposed to account for the changes observed in the chemical analysis of refractories.

The Rotating-Stall (RS) through a rotor-cascade of an axial compressor were numerically investigated with an unsteady two-dimensional finite-volume density based computer code. To validate the computer code, a test case was prepared and the good agreement of the compared results has given the adequate assurance of the code. The RS was incepted with a 40% reduction in flow coefficient and a 0.4% increase in the load coefficient from their normal operating values. The velocity traces from numerical probes, for all chosen number of blades had a periodic behavior, during RS effect. It was also concluded that the captured modal characteristics of RS may vary with varying the number of blades and this variation may cause various modes of RS. Moreover, in each mode, decreasing the number of blades may cause phase lag times in stall progress. In studied cases, approximately two modes and a transient mode were captured which had different rotational speeds and modal characteristics. Finally, a minimum required number of the blades for the RS inception studies (in spite of large numbers in previous works) was proposed, to intensify the probability of using shorter cascades in stability margin calculations of a compressor.

(The flow field associated with the passage of the turbulent spot in a 3–D duct with streamline divergence under zero pressure gradients was investigated and displayed as contour plots of the velocity perturbation in plan and elevation view of the spot. It suggests that, streamline divergence has no strong effect on the internal structure of the spot and eddies and their propagation in the downstream direction is similar to 2–D flows. The orthographic views are also shown. They are rather similar to contour plots but with different kind of presentation to show velocity excess and deficit as peaks and valleys respectively in the flow field while passage of the spot. This work was a part of detailed investigation of the structure of a distorted turbulent spot in a 3–D constant pressure flow

This study involved preliminary laboratory test work to identify the relative leaching response to cyanidation and thiourea leaching of an oxidized low grade gold ore based on characterization studies. Huge reserves of gold deposits have been reported from different parts of Iran, especially at Neishaboor area with gold grade of approx 4 ppm. For the mineralogical composition, the nature of the minerals, type of gold, chemical characters and the suitable mesh of grind which play vital role in finding out suitable flow sheet design, the representative samples were subjected to detailed characterization studies and found that, the ore is oxidized and gold is present partly in the from of solution in quartz veins as well as in the form of free particles in iron hydroxide specially hematite which is the product of pyrite oxidation. Quartz, hematite, calcite and feldspar are the main minerals present in the order of abundances. Sieve analysis and distribution of gold particles in different sieve fractions shows most of the gold are distributed bellow 2000 microns. Therefore based on characterization studies, the potential of an alternative lixiviant like thiourea leach have been determined and found that under optimized conditions cyanide leaching of the ore performs(extraction of 95% after 240 hours) better than thiourea leaching (extraction of 10% after 240 hours and 67% after 662 hours).