فهرست مطالب

Sciences, Islamic Republic of Iran - Volume:28 Issue: 3, Summer 2017

Journal of Sciences, Islamic Republic of Iran
Volume:28 Issue: 3, Summer 2017

  • تاریخ انتشار: 1396/06/19
  • تعداد عناوین: 7
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  • F. Nazari, Me. Kefayati, J. Raheb* Pages 205-219
    Combustion of sulfur components of fossil fuels such as oil causes the emission of SO2 in the atmosphere and lead to the formation of acidic rain in the environment. The conventional approach for desulfurization of fossil fuels is the chemical procedure of hydrodesulfurization (HDS). However, this method has low efficiency for desulfurization of ring components of sulfur such as dibenzothiophene (DBT) that include a significant percentage of the total sulfur content of fossil fuel. biodesulfurization (BDS), is a biological method proposed for desulfurization of ring components of sulfur which is a non-destructive pathway to remove sulfur from hydrocarbons of petroleum in the mild conditions which potentially used as complementary with HDS. For industrial application of BDS, the approach needs the new challenge to enhance desulfurization activity by genetic engineering methods and bioreactor development to achieve from a fantasy technique to an industrial and reality method for reduction of sulfur from fossil fuels. In this review, we studied and evaluated the BDS and advances in the two last decades.
    Keywords: biodesulfurization, Hydrodesulfurization, dibenzothiophene, Fossil fuels
  • S. Fozooni *, H. Khoshdast, H. Hassani, H. Hamidian Pages 221-230
    A new catalyst was prepared by promoting fly ash with hydrogen peroxide. The catalytic activity of H2O2 promoted fly ash (HPFA) was evaluated by synthesis 5(4H)-oxazolone and imidazolone derivatives under solvent free conditions. The possible mechanisms of synthesis reactions were also suggested. These proposed methods benefit in terms of low-cost catalyst, high yields, ease of workup, survival of different functional groups, reusability of the catalyst and short reaction time. These advantages render HPFA to be a promising catalyst for synthesis of organic materials.
    Keywords: Imidazolone, microwave irradiation, Oxazolone, H2O2 promoted fly ash, Solvent-free
  • A. Jamshidi *, M.R. Nikudel, M. Khamehchiyan, A. Zalooli, H. Yeganehfar Pages 231-241
    Salt crystallization is one of the most powerful weathering agents that may cause a rapid change in the mechanical properties of stones, and thus limit their durability. Consequently, determining the mechanical properties of stones due to salt crystallization is important for natural building stones used in marine environmental and mild climatic conditions, which expose excessive salt crystallization cycles. In this study, multivariate regression analysis was performed for estimating the mechanical properties of travertine building stones after salt crystallization test. For this purpose, 12 travertine samples were selected and their physical and mechanical properties (density, porosity, uniaxial compressive strength, Brazilian tensile strength, and P-wave velocity) were determined. Then salt crystallization test was carried out at sodium sulfate solution (Na2SO4) up to 50 cycles and, after every 5 cycles, the uniaxial compressive strength, Brazilian tensile strength and P-wave velocity of the samples were measured. Using data analysis, regression equations were developed for estimating the mechanical properties of deteriorated samples at any cycle of the salt crystallization test. In these equations, the mechanical properties of the samples after salt crystallization were considered to be the dependent variable, which is dependent on the independent variables of the number of salt crystallization cycles, initial mechanical properties of the stones and their porosities. The validity of the equations was verified with the mechanical properties data of a researcher for salt crystallization test. The results showed that regression equations are in good accuracy for estimating the mechanical properties of stones, and thus making a rapid durability assessment.
    Keywords: Salt crystallization, Uniaxial Compressive Strength, Brazilian tensile strength, P-wave velocity, Regression equations
  • M. Moazzen *, R. Michaeli, M. Ahangari, U. Altenberger Pages 243-253
    Metapelitic rocks in the Gasht area include micaschist, kyanite schist, andalusite schist, garnet schist, staurolite schist, cordierite schist and sillimanite schist. Tourmaline occurs as accessory mineral in all of these rock types. These schists are metamorphosed regionally and are affected by contact metamorpism subsequently. Based on the textural relations and the fact that CaO and TiO2 contents in the studied tourmalines are low, they are formed during regional metamorphism. They appear in the rock matrix and as inclusions in other minerals, especially biotite and albite. The studied tourmalines are of alkali type and are rich in dravite end-member. Cl and F contents are below the detection limit testifying for hydro-tourmaline nature of the studied minerals. Na and K are higher in the X-site in comparison with Ca. Low Ca shows neglegible amounts of Ca end-member or uvite. Mg content is much higher than Fe in the structure of the studied tourmalines, which are not zoned or show weak zoning and are grown at nearly constant P-T conditions. These tourmalines are crystallized from pelitic to psammitic protoliths in equlibrium with a fluid phase, rich in Al. Boron in fluid more likely was from the boron adsorbed on clay minerals surface in the protolith, released during metamorphism and boron from B-bearing mica breakdown during high tempertaure metamorphism, while boron released from the subducting oceanic crust is not a likely source for tourmaline crystallization in the studied rocks since there is no evidence for tourmaline in the associated oceanic crust mafic rocks.
    Keywords: Tourmaline, Dravite, Metapelites, Metamorphic Fluids
  • M. Yavari, M. Yazdi *, H. Ghalavand, M. H. Adabi Pages 255-265
    The Lower Cretaceous Carbonate deposits of the Dariyan Formation of the High Zagros Belt are mainly composed of thick to medium bedded limestone. These deposits contain abundant and diversified benthic foraminifera which have been recovered from carbonate rocks. A rich assemblage of microfossils with characteristic: Palorbitolina lenticularis (Blumenbach), Mesorbitolina subconcava (Leymerie), Mesorbitolina texana (Roemer), Mesorbitolina parva (Douglass) Pseudocyclammina hedbergi (Maync), Archalveolina reicheli (de Castro), Praechrysalidina infracretacea Luperto Sinni, Chofatella decipiens (Schlumberger), Debarina hahonerensis (Fourcade, Raoul et Vila), Rumanoculina ponticuli (Neagu), Rumanoloculina pseudominima (Bartenstein et Kovatcheva), Istriloculina cf. elliptica (Iovcheva) indicate paleoenviromental conditions of shallow water carbonate sedimentation and Urgonian type facies. Based on microfossils distribution and biozones identification in study sections, the age of the Dariyan Formation is assigned late Barremian-early Albian. The microfossils assemblages are regarded to be comparable with the Urgonian-type fauna known from the peri-Mediterranean Tethys in the Barremian-Albian time interval.
    Keywords: Cretaceous, Dariyan Formation, Foraminifera, Urgonian, Zagros
  • M. Jabbari Nooghabi * Pages 267-272
    In this paper, we use two statistics for detecting outliers in exponentiated Pareto distribution. These statistics are the extension of the statistics for detecting outliers in exponential and gamma distributions. In fact, we compare the power of our test statistics based on the simulation study and identify the better test statistic for detecting outliers in exponentiated Pareto distribution. At the end, we describe an example from insurance company.
    Keywords: Exponentiated Pareto sample, Z statistic, Dixon's statistic, outliers, Upper outlier
  • I. Qasemzadeh Kolagar, H. Haj Seyyed Javadi *, M. Anzani Pages 273-285
    Wireless sensor networks are composed of very small devices, called sensor nodes, for numerous applications in the environment. In adversarial environments, the security becomes a crucial issue in wireless sensor networks (WSNs). There are various security services in WSNs such as key management, authentication, and pairwise key establishment. Due to some limitations on sensor nodes, the previous key establishment techniques are unsuitable for WSNs. To overcome these problems, researchers propose several key pre-distribution schemes. Our proposed approach uses a combinatorial framework in the hypercube-based (HB) scheme to pre-distribute keys to each sensor node. By this way, the number of common keys between two nodes in a wireless communication range increases. Therefore, the level of security in terms of resilience against node capture attack and the probability of re-establishing an indirect key will be improved.
    Keywords: wireless sensor network, Key pre-distribution, Hypercube, Balanced incomplete block design (BIBD), Dynamic key path discovery algorithm