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  • 1.
    Ghorbani, Mohammad
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Cauchy cluster process2013In: Metrika (Heidelberg), ISSN 0026-1335, E-ISSN 1435-926X, Vol. 76, no 5, p. 697-706Article in journal (Refereed)
    Abstract [en]

    In this paper we introduce an instance of the well-know Neyman–Scott cluster process model with clusters having a long tail behaviour. In our model the offspring points are distributed around the parent points according to a circular Cauchy distribution. Using a modified Cramér-von Misses test statistic and the simulated pointwise envelopes it is shown that this model fits better than the Thomas process to the frequently analyzed long-leaf pine data-set.

  • 2. Ghorbani, Mohammad
    Maximum Entropy-Based Fuzzy Clustering by Using L_1-norm Space2005In: Turkish Journal of Mathematics, ISSN 1300-0098, E-ISSN 1303-6149, Vol. 29, no 4, article id 9Article in journal (Refereed)
  • 3.
    Ghorbani, Mohammad
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Testing the weak stationarity of a spatio-temporal point process2013In: Stochastic environmental research and risk assessment (Print), ISSN 1436-3240, E-ISSN 1436-3259, Vol. 27, no 2, p. 517-524Article in journal (Refereed)
    Abstract [en]

    A common assumption in analyzing spatial and spatio-temporal point processes is stationarity, while in many real applications because of the environmental effects the stationarity condition is not often met. We propose two types of test statistics to test stationarity for spatio-temporal point processes, by adapting, Palahi, Pukkala & Mateu (2009) and by considering the square difference between observed and expected (under stationarity) intensities. We study the efficiency of the new statistics by simulated data, and we apply them to test the stationarity of real data.

  • 4.
    Ghorbani, Mohammad
    et al.
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    Cronie, Ottmar
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden; Biostatistics, School of Public Health and Community Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden.
    Mateu, Jorge
    Department of Mathematics, University Jaume I, Castellon, Spain.
    Yu, Jun
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    Functional marked point processes: a natural structure to unify spatio-temporal frameworks and to analyse dependent functional data2020In: Test (Madrid), ISSN 1133-0686, E-ISSN 1863-8260, Vol. 30, no 3, p. 529-568Article in journal (Refereed)
    Abstract [en]

    This paper treats functional marked point processes (FMPPs), which are defined as marked point processes where the marks are random elements in some (Polish) function space. Such marks may represent, for example, spatial paths or functions of time. To be able to consider, for example, multivariate FMPPs, we also attach an additional, Euclidean, mark to each point. We indicate how the FMPP framework quite naturally connects the point process framework with both the functional data analysis framework and the geostatistical framework. We further show that various existing stochastic models fit well into the FMPP framework. To be able to carry out nonparametric statistical analyses for FMPPs, we study characteristics such as product densities and Palm distributions, which are the building blocks for many summary statistics. We proceed to defining a new family of summary statistics, so-called weighted marked reduced moment measures, together with their nonparametric estimators, in order to study features of the functional marks. We further show how other summary statistics may be obtained as special cases of these summary statistics. We finally apply these tools to analyse population structures, such as demographic evolution and sex ratio over time, in Spanish provinces. 

  • 5.
    Ghorbani, Mohammad
    et al.
    Department of mathematics and mathematical statistics, Umeå University, Sweden.
    Mateu, Jorge
    Department of Mathematics, Jaume I University, Castellón, Spain.
    A new class of spatial covariance functions generated by higher-order kernelsManuscript (preprint) (Other academic)
  • 6.
    Ghorbani, Mohammad
    et al.
    Department of Mathematics and Mathematical Statistics, Umeå University, Sweden.
    Vafaei, Nafiseh
    Department of Computer and Statistics Sciences, Faculty of Sciences, Mohaghegh Ardabili University, Ardabil, Iran.
    Dvořák, Jiří
    Department of Probability and Mathematical Statistics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
    Myllymäki, Mari
    Natural Resources Institute Finland (Luke), Helsinki, Finland.
    Testing the first-order separability hypothesis for spatio-temporal point patterns2021In: Computational Statistics & Data Analysis, ISSN 0167-9473, E-ISSN 1872-7352, Vol. 161, article id 107245Article in journal (Refereed)
    Abstract [en]

    First-order separability of a spatio-temporal point process plays a fundamental role in the analysis of spatio-temporal point pattern data. While it is often a convenient assumption that simplifies the analysis greatly, existing non-separable structures should be accounted for in the model construction. Three different tests are proposed to investigate this hypothesis as a step of preliminary data analysis. The first two tests are exact or asymptotically exact for Poisson processes. The first test based on permutations and global envelopes allows one to detect at which spatial and temporal locations or lags the data deviate from the null hypothesis. The second test is a simple and computationally cheap X2-test. The third test is based on stochastic reconstruction method and can be generally applied for non-Poisson processes. The performance of the first two tests is studied in a simulation study for Poisson and non-Poisson models. The third test is applied to the real data of the UK 2001 epidemic foot and mouth disease.

  • 7.
    Møller, J.
    et al.
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Ghorbani, Mohammad
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Functional summary statistics for the Johnson–Mehl model2015In: Journal of Statistical Computation and Simulation, ISSN 0094-9655, E-ISSN 1563-5163, Vol. 85, no 5, p. 899-916Article in journal (Refereed)
    Abstract [en]

    The Johnson–Mehl germination-growth model is a spatio-temporal point process model which among other things have been used for the description of neurotransmitters datasets. However, for such datasets parametric Johnson–Mehl models fitted by maximum likelihood have yet not been evaluated by means of functional summary statistics. This paper therefore invents four functional summary statistics adapted to the Johnson–Mehl model, with two of them based on the second-order properties and the other two on the nuclei-boundary distances for the associated Johnson–Mehl tessellation. The functional summary statistics theoretical properties are investigated, non-parametric estimators are suggested, and their usefulness for model checking is examined in a simulation study. The functional summary statistics are also used for checking fitted parametric Johnson–Mehl models for a neurotransmitters dataset.

  • 8.
    Møller, Jesper
    et al.
    Department of Mathematical Sciences, Aalborg University.
    Ghorbani, Mohammad
    Department of Mathematical Sciences, Aalborg University.
    Aspects of second-order analysis of structured inhomogeneous spatio-temporal point processes2012In: Statistica Neerlandica, ISSN 0039-0402, E-ISSN 1467-9574, Vol. 66, no 4, p. 472-491Article in journal (Refereed)
    Abstract [en]

    Statistical methodology for spatio-temporal point processes is in its infancy. We consider second-order analysis based on pair correlation functions and K-functions for general inhomogeneous spatio-temporal point processes and for inhomogeneous spatio-temporal Cox processes. Assuming spatio-temporal separability of the intensity function, we clarify different meanings of second-order spatio-temporal separability. One is second-order spatio-temporal independence and relates to log-Gaussian Cox processes with an additive covariance structure of the underlying spatio-temporal Gaussian process. Another concerns shot-noise Cox processes with a separable spatio-temporal covariance density. We propose diagnostic procedures for checking hypotheses of second-order spatio-temporal separability, which we apply on simulated and real data.

  • 9.
    Møller, Jesper
    et al.
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark Denmark.
    Ghorbani, Mohammad
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Rubak, Ege
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Mechanistic spatio-temporal point process models for marked point processes, with a view to forest stand data2015In: Biometrics, ISSN 0006-341X, E-ISSN 1541-0420, Vol. 72, no 3, p. 687-696Article in journal (Refereed)
  • 10.
    Rodríguez-Corté, Francisco J.
    et al.
    Department of Mathematics, Universitat Jaume I, Castellón, Spain.
    Ghorbani, Mohammad
    Department of Mathematical Sciences, Aalborg University, Aalborg, Denmark.
    Mateu, Jorge
    Department of Mathematics, Universitat Jaume I, Castellón, Spain.
    Stoyan, Dietrich
    Institut für Stochastik, TU Bergakademie Freiberg, Freiberg, Germany.
    On the expected value and variance for an estimator of the spatio-temporal product density function2014Report (Other academic)
  • 11.
    Vafaei, Nafiseh
    et al.
    Department of Computer and Statistics Sciences, Faculty of Sciences, University of Mohaghegh Ardabili, Ardabil, Iran.
    Ghorbani, Mohammad
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Ganji, Masoud
    Department of Computer and Statistics Sciences, Faculty of Sciences, University of Mohaghegh Ardabili, Ardabil, Iran.
    Myllymäki, Mari
    Natural Resources Institute Finland (Luke), Helsinki, Finland.
    Spatio-temporal determinantal point processesManuscript (preprint) (Other academic)
    Abstract [en]

    Determinantal point processes are models for regular spatial point patterns, with appealingprobabilistic properties. We present their spatio-temporal counterparts and give examples ofthese models, based on spatio-temporal covariance functions which are separable and non-separablein space and time.

  • 12.
    Vosoughi, Armin
    et al.
    Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran.
    Sadigh-Eteghad, Saeed
    Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
    Ghorbani, Mohammad
    Faculty of Mathematics, University of Tabriz, Tabriz, Iran.
    Shahmorad, Sedaghat
    Faculty of Mathematics, University of Tabriz, Tabriz, Iran.
    Farhoudi, Mehdi
    Neurosciences Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
    Rafi, Mohammad A.
    Department of Neurology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
    Omidi, Yadollah
    Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.
    Mathematical Models to Shed Light on Amyloid-Beta and Tau Protein Dependent Pathologies in Alzheimer’s Disease2020In: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 424, p. 45-57Article in journal (Refereed)
1 - 12 of 12
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