AMIRKABIR
Year:2004 | Volume:15 | Issue:59-D|Papers Count:13

In this study, the protective performance of zinc chromate at various PVCs (Pigment Volume Concentration = 25,30,35, 40, 45, 50) in epoxy ester resin is evaluated through electrochemical impedance technique. The obtained data is compared with those of routine tests, including, adhesion and salt spray fog chamber. The results show that in electrolyte with 3.5 % sodium chloride content, the values of log Z decrease for the samples exposed to salt spray for 24 hours, compared to the blank, while the behavior of samples exposed to salt spray chamber for two weeks increase it. These findings indicate that the impedance value changes in inverse proportion to the amount of water absorption, dielectric constant, and electrical capacitance of the coating. The results imply that the: best performance of this primer is in the PVC range of 30-40.

The set covering problem (SCP) is one of the location -allocation models. It s objective is to minimize the cost of facilities location-allocation in an optimal structure in such a way that each customer or zone has been covered by at least one facility. The above problem is a class of NP-Hard problems that cannot be solved by exact algorithms in a reasonable amount of computational time. Thus in this paper, a simulated annealing (SA) algorithm is proposed to solve the SCP. This algorithm is one of the efficient metaheuristics based on a neighbourhood search within solution space, acceptance of probability, and inferior solutions to scape from trap (i.e., local optimal solution). Ten test problems are solved in which associated results show the efficiency and validity: of the SA algorithm for solving the SCP. The validity comparisions of the results obtained the proposed algorithm are compared with the results reported by three methods named as Lingo 8 Software, Heragu's heuristic, and Genetic Algorithms (GAs).

Excavation of the underground spaces of Masojed Solaiaman Dam and its hydro-electric power plant cavern is performed by drilling and blasting. In order to reduce the ground vibration to a safe level, the peak particle velocity in the surrounding area was recorded, for the first 30 shots, by installing geophone in various locations. The recorded data were used for establishing a criterion for vibration control in future excavation works in the project.A number of empirical criteria are available in literature for ground vibration estimation. In this study, the applicability of 5 well known criteria was assessed using the recorded data and other relevant information. Correlations of all these equations with real data were quantified by means of a capable data analyzing software. The result of these analysis showed that, there was not great differences between the applicability of the existing equations, although .one of them was more applicable than the others. In other words, even the most applicable one of the five selected criteria did not demonstrate a satisfactory correlation with the recorded data.Further investigation towards developing a more reliable equation resulted in introducing a new equation for this project, which carries a much more accurate estimation of the vibration than any of the existing criteria. Therefore, the most suitable equation for the current project was introduced. The best values of the site specific parameters of the suggested equation, for minimization of the ground vibration, were determined. The suggested equation was applied to the data and its best fit was found for which the coefficient of correlation was 0.8919. The maximum instantaneous charge, producing a certain value of vibration intensity, can be calculated through the suggested equation and thus the vibration can be kept at the certain desired value.

In this research work, composite brazing sheets of 3003/4043 aluminum alloys were made by cold roll bonding. Peel test specimens were prepared from the welded composites and annealed in 400°C for 20-80 min. Bonding strength of the brazing sheets was measured by peel test. Maximum peeling strength was obtained under 70 % reduction in area after annealing for 40 min at 400°C.

Surface simulation is one of the important aspects in different engineering fields. Here, a new method of surface simulation, using fractal theory, with its application in surface mapping is presented.In this work, a computer software was developed to calculate the fractal dimension of surfaces using three different methods: motion and 2D motion dividers and variogram. The mid point movement method was used to generate new surfaces from an original surface while the fractal dimension of the new surface was kept to be equivalent to the original surface. This means that by using this technique the geometry of the generated surfaces are as close as possible to the original surface. This is the advantage of this method. For example using kriging estimator the simulated surfaces are smoother titan tlte original surface, which means a smaller fractal dimension.

Dalan (Upper Permian) and Kangan (Lower Triassic) Formation were deposited in an extensive carbonate platform under an arid climate. These formations makes up the essential part of the Gas reservoirs in south of Iran and Persian Gulf. Detailed field and petrographic investigation of over 1200 meter carbonate sequence of the Kangan and Dalan led to the recognition of several shallow marine (tidal flat, sabtidal, lagoon, bar and open marine) fades. Environment of deposition of these limestone were a Showalling -upward. The transition from Dalan to Kangan denotes a period of drastic change in the deposition environment and the chemical milieu of the sedimentation basin. These changes are reflected by a marked positive excursion of carbon and oxygen isotopes from Kangn to Dalan formation. Petrographic, chemical and isotopic studies of the dolomite in the Kangan and Dalan formations reveal that dolomitization was the result of several diagenetic events.The neomorphic alteration of these dolomites significantly modified their original chemical signatures. Dolomite in the Kangan and Dalan formed in two stages by different mechanisms in Dalan formation dolomitization occur in the early phase of syngenetic (penecontemporaneous) replacement of the pre-existing carbonate in an arid climate on a supratidal flat. Kangan's dolomite formed during deep burial.

This paper is devoted to seismotectonic of Bam region and surface refaulting associated with the destructive Bam earthquake of 26 December 2003. The earthquake with Magnitude 6. 7 Ms, shook Bam district, most of buildings were totally collapsed in Bam and surrounding villages and caused a lot of killed and injured people. From seismotectonic point of view, Bam located in a high active Zone involving a number of active faults. Bam fault is located in the extremely east-north part of this zone, which seems to be a tectonic tie. According to the macroseismic studies the causative source of the quake is Bam fault, which is a high angle fault and its trend is nearly N-S. The surface refaulting is about 9 kilometers long and the maximum residual strike slip displacement is 5 cm, which is left lateral. Bam city is situated on the west block of the fault and its distance to the fault zone is 1.5 km.

Weft insertion in weaving is an important subject, which has been studied by different research workers. A number of mechanisms have been invented, designed, manufactured, developed and Employed for this purpose. However, some of these systems have been commercialized. The present paper reports a magnetic weft inserting system, based on electromagnetic force, which was designed and manufactured as a model. Different features of the system and the parameters affecting in weft insertion are reported and discussed.

Band and Hardgrov methods are usually used in mineral processing industry for determining grindability of mineral materials . The Hardgrov method is often used for determining grindability of coal and materials that are grinded in the nntumbling mills. While the Bond method is used for determining grindability of other materials. Advantage of Bond method is to determine the amount of energy usage in comminution. While Hardgrov method is easy and no lendy method . In this study the control Screen have been changed for finer and coarser than the standard one (200 mesh).. in this paper the effect of this change on reloation between the Bond and Hardgrov grindabilities have been investigated and new equations are found. In this connection a sample of copper, iron and flouride ores along with control sxreens like 30,40, 60, 100 and 270 mesh were used. and final results are presented.

Based on the petrographical and petrochemical studies, it is suggested that the Sungun deposit as a composite stock, emplaced at a paleo-depth of ~2000 m, and comprising early monzonite/quartz- monzonite and a later diorite/granodiorite phase. The parental magma was a medium to high K andesite or diorite, initially contained >3 wt percent H2O (wet magma), and generated in continental arc settings. The high level emplacement of this magma, led to its saturation with water and the exsolution of fluids at an early stage of crystallization, and subsequently Mo and then Cu mineralization in the stock. Based on the major and trace element geochemistry, especially the behaviour of the immobile trace elements, Y, Zr and Nb, the fractional crystallization is suggested for the petrological characteristics of the present intrusive rocks. The degree of fractionation was estimated using a Rayleigh fractionation equation, which related the concentration of Zr, Nb and Y in the least altered sample to their concentrations in progressively more evolved samples. The results of these calculations indicated that the compositions of the various rock types can be explained by up to 24 % fractionation of a dioritic or andesitic magma to produce the more evolved monzonite/quartz-monzonite suite and chemically altered diorite-granodiorite suite.