فهرست مطالب

  • No. 2903, 2004
  • A3
  • تاریخ انتشار: 1383/07/15
  • تعداد عناوین: 18
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  • R. Aslaner Pages 341-347
    In this paper, the time-like hyperruled surfaces in the Minkowski 4-space and their algebraic invariants are worked. Also some characteristic results are found about these algebraic invariants.
    Keywords: Ruled surfaces, rulings, main curvature, scalar curvature, time, like vector
  • M. Barati, P. K. Ummat, G. Luke, W. R. Datars Pages 349-356
    The angular dependent magnetoresistance oscillation (ADMRO) of the stage-2 IBr graphite intercalation compound (GIC) was studied between 1.8 K and 110 K in magnetic fields between 1 and 9 T. There was a series of peaks in the c-axis resistance as the field direction was changed from the c axis to the (001) plane. The field independence of the angular positions of the peaks, showing that the oscillation is not from the Shubnikov-de Haas effect, and the presence of the oscillation at high temperatures indicate that the effect is semiclassic. The location and the relative amplitudes of the peaks show that the ADMRO in this compound does not follow the predictions for the symmetrical corrugation model of the cylindrical Fermi surface. The reason is attributed to the presence of two cylindrical Fermi surfaces and zone folding of the Fermi surface by the periodicity of the IBr lattice in this compound.
    Keywords: Graphite intercalation compound, ADMRO effect
  • B. Najafi, A. Tayebi, M. M. Rezaii Pages 357-366
    In this paper the general relatively isotropic L-curvature Finsler metrics are studied. It is shown that on constant relatively Landsberg spaces, the concepts of weakly Landsbergian, Landsbergian and generalized Landsbergian metrics are equivalent. Some necessary conditions for a relatively isotropic L-curvature Finsler metric to be a Riemannian metric are also found.
    Keywords: Finsler metric, (generalized) Landsberg metric, (mean) landsberg curavture, (mean) Cartan tensor, Douglas tensor, Funk metric, Randers metric
  • S. Fazlian, S. Sobhanian, A. Muradov Pages 367-375
    In the present paper axial distributions of plasma and floating potentials, electron and ion densities and EEDF have been measured in the DL region of a Hg discharge constriction. An attempt has been made for the resolution of opposing charged layer structures in DL. Excitation processes in the constriction region are studied. Using the linearization method for the nonstationary balance equations system and choosing appropriate discharge conditions, the step excitation rate by the electron impact for 63P2 71S0 transition in Hg is determined.
    Keywords: Double layers (DL), EEDF, plasma parameters, excitation processes, constriction edge, excitation rates, modulation depths, spectral lines
  • S. Nadarajah, S. Kotz Pages 377-385
    The Fisher information matrix for a mixture of two Pareto distributions is derived. Numerical tabulations of the matrix are also provided for practical purposes. The work is motivated by a real-life example.
    Keywords: Lerch function, pareto distribution
  • M. Zare, A. R. Nematollahi, M. Rahnemaei Pages 387-399
    Data monitoring is important in the study and analysis of hydrological behaviors of karstic systems. Monitoring shows the various regimes of groundwater flow (laminar or turbulent), depletion, filling, filtration and karstification degree of karst aquifers. In recent years, analyses of these data had considerable advances using stochastic time series analyses. An important problem related to these analyses is the constraint of financial and technical human support. If we can increase the time intervals, the costs are lowered and development of new monitoring networks will be possible. In this research, the effect of monitoring time intervals on the results of time series analysis and calculated hydrologic delay times are studied, using bivariate analyses in spectral domain. The first (shorter) and the second (longer) delay times are related to the flow of groundwater through the larger and smaller fractures of the karstic system, respectively. Daily groundwater level data of three piezometers and the discharge of a spring in the Maharlu karst basin in Iran (52o12'' to 53o28''E and 29o1'' to 30o6''N) were acquired and then six different time series having different time intervals (1, 3, 7, 10, 14 and 30 days) were extracted and analyzed. The results show that the variation of the computed stochastic parameters with increasing time intervals is unpredictable, but the variation of time (period) corresponding to the frequency at the peak of amplitude function (curve) shows a linear and predictable relationship, which is unique for every kind of karstic aquifer having different degrees of karstification.
    Keywords: Karst, time series, squared coherency, phase, amplitude, delay time
  • M. H. Mahdieh, M. Alavi, Nejad Pages 401-410
    Spatial distribution of electric field amplitude has an essential role in laser-induced damage multi-layer coating. A new method introduced in this paper to reduce the electric field intensity effectively within the high index layers in multi-layer reflectors that are irradiated by high power lasers. The design is based on specific non-quarter wave pairs, assuming the number of layers is held constant. Using a combination of periodic and non-periodic pairs of a non-quarter wave stack with an appropriate thickness for a specific angle of incidence, minimum electric field can be obtained within the high index layers for the S or P polarization. Different results can be obtained if the non-periodic pairs are placed adjacent to the substrate, or to the ambient. We have shown that by the former design, a lower electric field can be achieved within the layers and the mirror can be optimized. The optimization was carried out for oblique incidence and the effect of angle of incidence was examined for both S and P polarizations.
    Keywords: Optical multi, layers, high power laser mirrors, optical damage, electric field reduction
  • N. H. Halimi Pages 411-420
    The aim of this paper is to study orders over a valuation ring V with arbitrary rank in a central simple F-algebra Q. The relation between all of the orders is explained with a diagram. It is then shown that inside Bezout order, extremal V-orders are precisely semi-hereditary. In the last section, the effect of Henselization on maximal and semi-hereditary orders is examined.
    Keywords: Dubrovin valuation rings, extremal orders, Henselization
  • A. Ghasemizad, M. R. Eskandari, S. Khoshbinfar, M. Kamran Pages 421-431
    In isobaric models for inertial confinement fusion it is assumed that the target configuration at stagnation time (maximum compression) consists of two regions, hot spark and cold fuel, respectively. Here the conditions of spark formation and ignition in hydrogen equimolar isotopes in central spark ignition are investigated and permissible values of Hs and Ts are evaluated numerically. By introducing a dimensionless parameter, ψs, the class of targets are considered by the specific value of ψs. Finally, limiting fuel energy gain curve (Gf*) as a function of ignition energy (Eign) allows different implosion velocities to be calculated. This result is in good agreement with more complex hydrodynamic models.
    Keywords: Central spark ignition, spark parameter, isobaric model, limiting gain curve
  • J. Behboodian, A. Mohammadpour Pages 433-455
    The problem of hypothesis testing with a nuisance parameter is considered. Two methods for using fuzzy knowledge on the nuisance parameter to test hypotheses are suggested. These methods are neither a pure classical nor a pure Bayesian approach to hypothesis testing, but rather related to both. A few known examples and their applications, which cannot be studied by the parametric statistical methods, are discussed.
    Keywords: Fuzzy Statistics, defuzzified distribution, weighted defuzzification, Estimator, exchangeable normal Distribution
  • H. B. Karadag, S. Keles Pages 455-470
    In this paper, the dual area vector of a closed dual spherical curve is kinematically generated and the dual Steineer vector of a motion are extensively studied by the methods of differential geometry. Jacobi’s Theorems, known for real curves, are investigated for closed dual curves. The closed trajectory surfaces generated by an oriented line are fixed in a moving rigid body in IR3, in which the closed dual curves from E. Study’s transference principle is studied. The integral invariants of these closed ruled surfaces are calculated by means of the area vector. Moreover, some theorems, results and examples are given.
    Keywords: Mechanism, kinematics, area vectors, ruled surfaces, invariants, motions
  • K. Hadad, A. Safavi, R. Tahon Pages 471-480
    The air quality in Shiraz was assessed based on a one-week passive sampling campaign. During the first week of the summer 2003, about 400 passive samplers were used in groups of two and three, so that 187 sampling stations covered all of Shiraz. Pollutant gases including SO2, NO2 and BTX (benzene, toluene and xylene) were sampled by diffusive sampling tubes. Collected samples were analyzed and pollutant concentrations were determined by using ion chromatography, spectrophotometry and gas chromatography techniques. The result of the analysis shows that SO2 and NO2 concentrations exceed national and international standards in the central and southern parts of Shiraz. Weekly averaged concentrations of benzene, toluene and xylene at all sampling sites were 105, 206 and 123 mg/m3, which exceed national and international standards.Based on the results, more than 15% of Shiraz’s population (180,000 out of 1.2 million people) were exposed to high levels of NO2 during this survey period.
    Keywords: Urban air pollution, passive sampling, air quality, BTX concentration
  • F. Ayatollah Zadeh Shirazi Pages 481-495
    This text carries out some ideas about exact and P-exact sequences of transformation semigroups. Some theorems like the short five lemma (Lemma 1.3 and Lemma 2.3) are valid here as in exact sequences of R-modules.
    Keywords: a, minimal set, exact sequence, P, exact sequence, proximal relation, transformation semigroup
  • B. Najafi, A. Tayebi, M. M. Rezaii Pages 497-505
    The general relatively isotropic mean Landsberg metrics contain the general relatively isotropic Landsberg metrics. A class of Finsler metrics is given, in which the mentioned two concepts are equivalent. In this paper, an interpretation of general relatively isotropic mean Landsberg metrics is found by using C-conformal transformations. Some necessary conditions for a general relatively isotropic mean Landsberg metric, as well as generalized Landsberg metric to be a Riemannian metric are also found.
    Keywords: Finsler structure, Cartan connection, (generalized) Landsberg metric, scalar curvature, C2, like space, c, conformal transformation
  • M. N. Ghosseiri Pages 507-514
  • C. Tunc, E. Tunc Pages 515-521
    Sufficient conditions are established under which the zero solution X=0 of equation (2) is unstable
    Keywords: Nonlinear differential equations, seventh order, instability, Lyapunov's second (direct) method
  • A. Bazargan, Lari Pages 523-529
    The mean and variance of the Lagrangian Katz family of distribution (LKD), the basic Lagrangian Katz distribution of Type I (LKD-I) and Type II (LKD-II) are provided in an easy method. The recurrence relation between the non-central, central and factorial moments, and the recurrence relation between moments and cumulants of LKD, LKD-I and LKD-II are given. The first four cumulants of LKD-I and LKD-II are provided.
    Keywords: Lagrangian Katz Family of Distribution (LKD), recurrence relations, central, non, central, factorial moments, cumulants
  • S. Hedayatian, B. Bidabad Pages 531-539