فهرست مطالب

  • Volume:35 Issue:2, 2011
  • A2
  • تاریخ انتشار: 1390/07/05
  • تعداد عناوین: 10
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  • D. Heidari, B. Davvaz Pages 69-80
    The concept of  -semihypergroups is a generalization of semigroups, a generalization of semihypergroups and a generalization of  -semigroups. In this paper, we study the concept of semiprime ideals in a  -semihypergroup and prove some results. Also, we introduce the notion of  -hypergroups and closed  -subhypergroups. Finally, we study the concept of  -semihypergroups associated to binary relations and give necessary and sufficient conditions on a set of binary relations  on a non-empty set S such that S becomes a  -semihypergroup or a  -hypergroup.
  • A. H. Ansari, K. Alamdar Pages 81-88
    In order to obtain maximum information from magnetic and gravity anomaly maps, application of an edge detection method is necessary. In this regard two commonly used methods are derivative filters and local phase filters. In this paper, a MATLAB code is expanded to combine an analytic signal filter and a tilt angle filter as a new edge detection filter called ASTA filter. This method was demonstrated on synthetic magnetic data from 3 models and also on real magnetic and gravity data from southwest England. Findings show that the boundaries of a causative body are enhanced more accurately using this new filter, compared with other edge detection filters. The source code in MATLAB format is available from the authors on request.
  • E. Peyghan A. Ahmadi, A. Tayebi Pages 89-99
    A Cartan manifold is a smooth manifold M whose slit cotangent bundle 0T *M is endowed with a regular Hamiltonian K which is positively homogeneous of degree 2 in momenta. The Hamiltonian K defines a (pseudo)-Riemannian metric ij g in the vertical bundle over 0 T *M and using it, a Sasaki type metric on 0 T *M is constructed. A natural almost complex structure is also defined by K on 0 T *M in such a way that pairing it with the Sasaki type metric an almost Kähler structure is obtained. In this paper we deform ij g to a pseudo-Riemannian metric ij G and we define a corresponding almost complex Kähler structure. We determine the Levi-Civita connection of G and compute all the components of its curvature. Then we prove that if the structure (,, ) 0 T *M G J is Kähler- Einstein, then the Cartan structure given by K reduces to a Riemannianone.
  • Y. Rahimsouri, A. Yaghubpur, S. Modabberiand S. Alipou Pages 100-111
    The concentrations of potentially toxic elements (As, Sb, and Hg) and some trace elements in 36 topsoil samples and 18 agricultural soil samples were measured at the Aq-Darreh River watershed, NW Iran. Based on the results of the chemical analysis and comparing them with different standards, it seems that the soils of the Aq-Darreh River watershed are polluted with As and Sb. This pollution results from geochemical background (natural contamination) and mining activities. Geochemical background values in topsoil and agricultural soils were estimated for As (429.7 ppm and 98.8 ppm), Sb (79.02 ppm and 3.98 ppm), and Hg (356 ppb and 2596 ppb). This research also indicates that mining activities have played a significant role in soil pollution and increasing As, Sb and Hg concentration in topsoils and As and Sb in agricultural soils. Results of sequential leaches and XRD analyses of both soil types showed that most of the As concentration is bound to amorphous iron hydroxides in soils, while Sb and Hg are bound to resistant minerals such as stibnite and cinnabar. Clay and carbonate mineralshave a lower adsorption of these pollutant elements in both topsoil and agricultural soils.
  • M. Mardani Shahrbabak, A. A. Noura Pages 113-116
    Sueyoshi and Sekitani in 2007 presented a paper that explores the measurement of Returns to Scale under a possible occurrence of multiple solution in a reference set and a supporting hyperplane. The occurrence of multiple solutions is classified into Type I and Type II. Type I is an occurrence of multiple solutions in a reference set. Type II is an occurrence of multiple solutions on a supporting hyperplane passing on the reference set. In this paper we want to apply their method for estimating RTS under weight restrictions. For this goal we use tone’s method for estimating RTS under weight restrictions.
  • M. M. Ebrahimi, M. Mahmoudi Pages 117-124
    The ordinary tensor product of modules is defined using bilinear maps (bimorphisms), that are linear in each component. keeping this in mind, Linton and Banaschewski with Nelson defined and studied the tensor product in an equational category and in a general (concrete) category K, respectively, using bimorphisms, that is, defined via the Hom-functor on K. Also, the so-called sesquilinear, or one and a half linear maps and the corresponding tensor products generalize these notions for modules and vector spaces. In this paper, taking a concrete category K and an arbitrary subfunctor H of the functor U¢ = Hom  (Uop ´U) rather than just the Hom-functor, where U is the underlying set functor on K, we generalize sesquilinearity to bivariation and study the related notions such as functional internal lifts, universal bivariants, tensor products, and their interdependence.
  • B. Rezaei, M. Rafie-Rad Pages 125-130
    In this paper, the Matsumoto metric with special Ricci tensor has been investigated. It is proved that, if  is of positive (negative) sectional curvature and F is of  -parallel Ricci curvature with constant killing 1-form, then (M,F) is a Riemannian Einstein space. In fact, we generalize the Riemannian result established by Akbar- Zadeh.
  • S. Yaghoubi, S. Noori, M. Bagherpour Pages 131-147
    In this research, both resource allocation and reactive resource allocation problems in multi-server dynamic PERT networks are analytically modeled, where new projects are expected to arrive according to a Poisson process, and activity durations are also known as independent random variables with exponential distributions. Such system is represented as a queuing network, where multi servers at each service station are allocated, and also each activity of a project is operated at a devoted service station with only one server located at a node of the network based on First Come First Serve (FCFS) policy. In order to propose a novel approach for modeling of multi-server dynamic PERT network, initially the network of queues is transformed into a stochastic network. Then, a differential equations system is organized to solve and obtain approximate completion time distribution for any particular project by applying an appropriate finite-state continuous-time Markov model. Finally, a multi-objective model including four conflicted objectives is presented to optimally control the resources allocated to the service stations in a multi-server dynamic PERT network, and the goal attainment method is further employed to solve a discretetime approximation of the primary multi-objective problem.
  • N. Mehdipour, M. Fallahi, G. Azari Takami, G. Vossoughi, A. Mashinchian Pages 157-163
    One of the most important aims of aquatic hatcheries is availability to mass produce of Daphnia magna as a livefood with high nutritional value in the shortest time. In the present study, D. magna fed with two freshwater greenalgae species, Chlorella sp. and Scenedesmus obliquus, enriched with different dosages of a mixture B group vitamins (0, 0.5, 1 and 2 ml.l-1) were compared at two stages (at the beginning of the culture and at the end of logarithmic growth phase). The results showed that increases in the B group vitamin levels in both enriched algae performed, increasing the fecundity and population growth rate in D. magna at the two compared stages, but significantly only with the control group (P<0.05). The highest fecundity and population growth rate obtained in D. magna was when they were fed algae enriched with 2 ml.l -1, but not significantly with 0.5 and 1 ml.l -1(P>0.05).