Oki Neswan - Academia.edu (original) (raw)

Papers by Oki Neswan

Research paper thumbnail of Beberapa Aplikasi dari Ultraproducts di Dalam Teori Model

Jurnal Matematika & Sains, Jul 10, 2009

Research paper thumbnail of Estimation of the parameters of isotropic semivariogram model through bootstrap

Applied mathematical sciences, 2015

In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partit... more In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partitioning its range. By conducting simulation, a semivariogram model with previously given parameters will be estimated through bootstrap method. Least square-bootstrap (LS-Bootstrap) will be applied to estimate the parameters of the model after resampling the errors of the model. The selection of the resulting semivariogram model from bootstrap method will be affected by the number of distance lags, the precision level of the range partitions, the number of bootstrap iterations, and the given reference model. The exponential and Gaussian models are sufficiently good in the estimation for the models with the same references. Meanwhile, the estimation yielded from spherical model is quite far from the reference 5124 K. N. Sari et al. exponential and Gaussian models, with the mean square error value reaching 713. The estimation with bootstrap method which is the same as the reference model will be faster to converge with the maximum iteration of 50. Besides, bootstrap method enables to obtain the point estimates and interval estimates of the nugget effect, sill, and range parameters.

Research paper thumbnail of Estimating Copula-Based Extension of Tail Value-at-Risk and Its Application in Insurance Claim

Risks, May 30, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of n-Normed Spaces with Norms of Its Quotient Spaces

Journal of physics, Sep 1, 2018

The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characte... more The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characteristics of n-normed spaces have been discussed by many researchers. These spaces are usually observed using a set of n linear independent vectors. In this paper, we will construct quotient spaces of an n-normed space with respect to n linear independent vectors. We define a norm in each quotient space by using the n-norm that we have. Norms of these quotient spaces will be a new viewpoint in observing characteristics of n-normed spaces.

Research paper thumbnail of On topological integer additive set-labeling of star graphs

EJGTA : Electronic Journal of Graph Theory and Applications, Oct 10, 2018

For integer k ≥ 2, let X = {0, 1, 2,. .. , k}. In this paper, we determine the order of a star gr... more For integer k ≥ 2, let X = {0, 1, 2,. .. , k}. In this paper, we determine the order of a star graph K 1,n of n + 1 vertices, such that K 1,n admits a topological integer additive set-labeling (TIASL) with respect to a set X. We also give a condition for a star graph K 1,n such that K 1,n is not a TIASL-graph on set X.

Research paper thumbnail of Perluasan Masalah Isoperimetrik pada Bangun Ruang

Jambura Journal of Mathematics

In this paper, several extensions of the isoperimetric problem in solid figures are explored, foc... more In this paper, several extensions of the isoperimetric problem in solid figures are explored, focusing on oblique and right prisms with rectangular, right-angled triangular, and regular hexagonal bases. The objective of this research is to find the prism with the largest volume while keeping the surface area constant. Through manipulations of algebra and simple trigonometry, evidence is obtained that a right prism provides a larger volume than an oblique prism if their surface areas are equal. By utilizing partial derivatives of a two-variable function and the Lagrange multiplier method, conditions for the side lengths are derived to obtain the prism with the maximum volume. The results show that a cube is the solution to the isoperimetric problem, meaning it has the largest volume among prisms with rectangular bases, while for the isoperimetric solution on prisms with right-angled triangular bases, the base of the prism must be an isosceles right-angled triangle. A regular hexagona...

Research paper thumbnail of Simulation of angle on geometry anisotropic semivariogram modeling in the case of oil in Jatibarang reservoir

Nucleation and Atmospheric Aerosols, 2015

Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a ... more Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a pair of wells has important function in defining the spatial correlation between wells. In geometry anisotropic, function of range is formulated in trigonometric functions of the angle between pairs of wells that have periodicity property. The fluctuations of range will affect on shifting geometry anisotropic models with different properties for each quadrant of angle. In three semivariogram models (exponential, spherical and gaussian), the increasing of angle give difference influence for range function and the shifting of semivariogram value.

Research paper thumbnail of Dasar-dasar Teori Model Tanpa Tanda Kesamaan

Jurnal Matematika & Sains, Aug 10, 2009

... Kemudian hasil-hasil yang diperoleh memperlihatkan banyak kesejajaran dengan teori model dima... more ... Kemudian hasil-hasil yang diperoleh memperlihatkan banyak kesejajaran dengan teori model dimana tanda kesamaan = diasumsikan ada dalam С 2 Konstruksi Sintaktis Misal кап С adaiah bahasa orde pertama tan pa tanda kesamaan yang memuat tiga macam simbol у ai tu ...

Research paper thumbnail of Estimation of the parameters of isotropic semivariogram model through bootstrap

Applied Mathematical Sciences, 2015

In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partit... more In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partitioning its range. By conducting simulation, a semivariogram model with previously given parameters will be estimated through bootstrap method. Least square-bootstrap (LS-Bootstrap) will be applied to estimate the parameters of the model after resampling the errors of the model. The selection of the resulting semivariogram model from bootstrap method will be affected by the number of distance lags, the precision level of the range partitions, the number of bootstrap iterations, and the given reference model. The exponential and Gaussian models are sufficiently good in the estimation for the models with the same references. Meanwhile, the estimation yielded from spherical model is quite far from the reference 5124 K. N. Sari et al. exponential and Gaussian models, with the mean square error value reaching 713. The estimation with bootstrap method which is the same as the reference model will be faster to converge with the maximum iteration of 50. Besides, bootstrap method enables to obtain the point estimates and interval estimates of the nugget effect, sill, and range parameters.

Research paper thumbnail of The copula-based conditional tail moments for new Pareto-type distribution

2021 ASIA-PACIFIC CONFERENCE ON APPLIED MATHEMATICS AND STATISTICS

Research paper thumbnail of Estimating Copula-Based Extension of Tail Value-at-Risk and Its Application in Insurance Claim

Risks

Dependent Tail Value-at-Risk, abbreviated as DTVaR, is a copula-based extension of Tail Value-at-... more Dependent Tail Value-at-Risk, abbreviated as DTVaR, is a copula-based extension of Tail Value-at-Risk (TVaR). This risk measure is an expectation of a target loss once the loss and its associated loss are above their respective quantiles but bounded above by their respective larger quantiles. In this paper, we propose nonparametric estimators for DTVaR and establish their property of consistency. Moreover, we also propose the variability measure around this expected value truncated by the quantiles, called the Dependent Conditional Tail Variance (DCTV). We use this measure for constructing confidence intervals of the DTVaR. Both parametric and nonparametric approaches for DTVaR estimations are explored. Furthermore, we assess the performance of DTVaR estimations using a proposed backtest based on the DCTV. As for the numerical study, we take an application in the insurance claim amount.

Research paper thumbnail of Spektrum Gstar(1;1)

In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) mo... more In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) model by considering the model as VMA( ∞ ). The spectrum can be obtained by following steps: represent the model as an VMA( ∞ ) and convert the model to the backward operator form, then substitute the coefficient model to the spectrum of VMA( ∞ ) model. The procedure of finding spectrum of GSTAR(1;1) which parameters are given, is illustrated by a two dimensional GSTAR(1;1) model.

Research paper thumbnail of n-Normed Spaces with Norms of Its Quotient Spaces

Journal of Physics: Conference Series, 2018

The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characte... more The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characteristics of n-normed spaces have been discussed by many researchers. These spaces are usually observed using a set of n linear independent vectors. In this paper, we will construct quotient spaces of an n-normed space with respect to n linear independent vectors. We define a norm in each quotient space by using the n-norm that we have. Norms of these quotient spaces will be a new viewpoint in observing characteristics of n-normed spaces.

Research paper thumbnail of Mechanical Properties and Microstructure at Stainless Steel HAZ from Dissimilar Metal Welding After Heat Treatment Processes

IOP Conference Series: Materials Science and Engineering, 2019

Metallurgy of HAZ at both metals after dissimilar metal welding is important to be evaluated, bec... more Metallurgy of HAZ at both metals after dissimilar metal welding is important to be evaluated, because differences in metallurgical characteristics due to heating effect on bothHAZ might take place after the process. For the case of austenitic stainless steel, metallurgical aspects that should be considered after welding are the formation of chromium carbide (sensitization) and delta ferrite phase. In the present research, focus is given on the HAZ microstructure and hardness both after welding and post-heat treatment process. Microstructure observation was carried out by optical microscope and Scanning Electron Microscope (SEM), whereas hardness testing was carried out by micro-Vickers method. From this study, it can be concluded that the increase in heat treatment temperature can reduce the volume fraction of delta ferrite and chrome carbide precipitation, whereas hardness at the HAZ region decreases after the heat treatment.

Research paper thumbnail of A formula for the g-angle between two subspaces of a normed space

Beiträge zur Algebra und Geometrie / Contributions to Algebra and Geometry, 2017

We develop the notion of g-angle between two subspaces of a normed space. In particular, we discu... more We develop the notion of g-angle between two subspaces of a normed space. In particular, we discuss the g-angle between a 1-dimensional subspace and a t-dimensional subspace for t ≥ 1 and the g-angle between a 2-dimensional subspace and a t-dimensional subspace for t ≥ 2. Moreover, we present an explicit formula for the g-angle between two subspaces of ℓ p spaces.

Research paper thumbnail of Konstruksi Interpolator Morfologi Biner 2D Dengan Metrik Hausdorfi

Dalam Matematika Morfologi, interpolasi gambar biner dipandang sebagai masalah interpolasi pada h... more Dalam Matematika Morfologi, interpolasi gambar biner dipandang sebagai masalah interpolasi pada himpunan. Misalkan X dan Y adalah himpunan-himpunan yang menyatakan dua buah gambar biner 2D, maka interpolasi dari kedua gambar biner ini akan menghasilkan deretan gambar baru yang merupakan transformasi gam- bar biner pertama (X) ke gambar biner lainnya (Y ). Metode yang digunakan dalam interpolasi ini adalah dengan menggunakan metrik Hausdorfo h(X; Y ) = max supx2X d(x; Y ); supy2Y d(y;X) . Dalam tugas akhir ini akan dikonstruksi deretan fZfig, interpolator yang membentuk geodesik dengan memodifikasi metrik Hausdorfi oleh dilasi.

Research paper thumbnail of Beberapa Aplikasi dari Ultraproducts di Dalam Teori Model

Jurnal Matematika Sains, Jul 10, 2009

Research paper thumbnail of Simulation of angle on geometry anisotropic semivariogram modeling in the case of oil in Jatibarang reservoir

AIP Conference Proceedings, 2015

Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a ... more Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a pair of wells has important function in defining the spatial correlation between wells. In geometry anisotropic, function of range is formulated in trigonometric functions of the angle between pairs of wells that have periodicity property. The fluctuations of range will affect on shifting geometry anisotropic models with different properties for each quadrant of angle. In three semivariogram models (exponential, spherical and gaussian), the increasing of angle give difference influence for range function and the shifting of semivariogram value.

Research paper thumbnail of Spektrum Gstar(1;1)

Jurnal Matematika Sains, Dec 10, 2009

In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) mo... more In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) model by considering the model as VMA( ∞ ). The spectrum can be obtained by following steps: represent the model as an VMA( ∞ ) and convert the model to the backward operator form, then substitute the coefficient model to the spectrum of VMA( ∞ ) model. The procedure of finding spectrum of GSTAR(1;1) which parameters are given, is illustrated by a two dimensional GSTAR(1;1) model.

Research paper thumbnail of Spektrum Gstar(1;1)

Jurnal Matematika dan Sains, 2008

In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) mo... more In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) model by considering the model as VMA(∞). The spectrum can be obtained by following steps: represent the model as an VMA(∞) and convert the model to the backward operator form, then substitute the coefficient model to the spectrum of VMA(∞) model. The procedure of finding spectrum of GSTAR(1;1) which parameters are given, is illustrated by a two dimensional GSTAR(1;1) model.

Research paper thumbnail of Beberapa Aplikasi dari Ultraproducts di Dalam Teori Model

Jurnal Matematika & Sains, Jul 10, 2009

Research paper thumbnail of Estimation of the parameters of isotropic semivariogram model through bootstrap

Applied mathematical sciences, 2015

In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partit... more In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partitioning its range. By conducting simulation, a semivariogram model with previously given parameters will be estimated through bootstrap method. Least square-bootstrap (LS-Bootstrap) will be applied to estimate the parameters of the model after resampling the errors of the model. The selection of the resulting semivariogram model from bootstrap method will be affected by the number of distance lags, the precision level of the range partitions, the number of bootstrap iterations, and the given reference model. The exponential and Gaussian models are sufficiently good in the estimation for the models with the same references. Meanwhile, the estimation yielded from spherical model is quite far from the reference 5124 K. N. Sari et al. exponential and Gaussian models, with the mean square error value reaching 713. The estimation with bootstrap method which is the same as the reference model will be faster to converge with the maximum iteration of 50. Besides, bootstrap method enables to obtain the point estimates and interval estimates of the nugget effect, sill, and range parameters.

Research paper thumbnail of Estimating Copula-Based Extension of Tail Value-at-Risk and Its Application in Insurance Claim

Risks, May 30, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of n-Normed Spaces with Norms of Its Quotient Spaces

Journal of physics, Sep 1, 2018

The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characte... more The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characteristics of n-normed spaces have been discussed by many researchers. These spaces are usually observed using a set of n linear independent vectors. In this paper, we will construct quotient spaces of an n-normed space with respect to n linear independent vectors. We define a norm in each quotient space by using the n-norm that we have. Norms of these quotient spaces will be a new viewpoint in observing characteristics of n-normed spaces.

Research paper thumbnail of On topological integer additive set-labeling of star graphs

EJGTA : Electronic Journal of Graph Theory and Applications, Oct 10, 2018

For integer k ≥ 2, let X = {0, 1, 2,. .. , k}. In this paper, we determine the order of a star gr... more For integer k ≥ 2, let X = {0, 1, 2,. .. , k}. In this paper, we determine the order of a star graph K 1,n of n + 1 vertices, such that K 1,n admits a topological integer additive set-labeling (TIASL) with respect to a set X. We also give a condition for a star graph K 1,n such that K 1,n is not a TIASL-graph on set X.

Research paper thumbnail of Perluasan Masalah Isoperimetrik pada Bangun Ruang

Jambura Journal of Mathematics

In this paper, several extensions of the isoperimetric problem in solid figures are explored, foc... more In this paper, several extensions of the isoperimetric problem in solid figures are explored, focusing on oblique and right prisms with rectangular, right-angled triangular, and regular hexagonal bases. The objective of this research is to find the prism with the largest volume while keeping the surface area constant. Through manipulations of algebra and simple trigonometry, evidence is obtained that a right prism provides a larger volume than an oblique prism if their surface areas are equal. By utilizing partial derivatives of a two-variable function and the Lagrange multiplier method, conditions for the side lengths are derived to obtain the prism with the maximum volume. The results show that a cube is the solution to the isoperimetric problem, meaning it has the largest volume among prisms with rectangular bases, while for the isoperimetric solution on prisms with right-angled triangular bases, the base of the prism must be an isosceles right-angled triangle. A regular hexagona...

Research paper thumbnail of Simulation of angle on geometry anisotropic semivariogram modeling in the case of oil in Jatibarang reservoir

Nucleation and Atmospheric Aerosols, 2015

Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a ... more Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a pair of wells has important function in defining the spatial correlation between wells. In geometry anisotropic, function of range is formulated in trigonometric functions of the angle between pairs of wells that have periodicity property. The fluctuations of range will affect on shifting geometry anisotropic models with different properties for each quadrant of angle. In three semivariogram models (exponential, spherical and gaussian), the increasing of angle give difference influence for range function and the shifting of semivariogram value.

Research paper thumbnail of Dasar-dasar Teori Model Tanpa Tanda Kesamaan

Jurnal Matematika & Sains, Aug 10, 2009

... Kemudian hasil-hasil yang diperoleh memperlihatkan banyak kesejajaran dengan teori model dima... more ... Kemudian hasil-hasil yang diperoleh memperlihatkan banyak kesejajaran dengan teori model dimana tanda kesamaan = diasumsikan ada dalam С 2 Konstruksi Sintaktis Misal кап С adaiah bahasa orde pertama tan pa tanda kesamaan yang memuat tiga macam simbol у ai tu ...

Research paper thumbnail of Estimation of the parameters of isotropic semivariogram model through bootstrap

Applied Mathematical Sciences, 2015

In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partit... more In isotropic semivariograms, ordinary least squares can estimate nugget effect and sill by partitioning its range. By conducting simulation, a semivariogram model with previously given parameters will be estimated through bootstrap method. Least square-bootstrap (LS-Bootstrap) will be applied to estimate the parameters of the model after resampling the errors of the model. The selection of the resulting semivariogram model from bootstrap method will be affected by the number of distance lags, the precision level of the range partitions, the number of bootstrap iterations, and the given reference model. The exponential and Gaussian models are sufficiently good in the estimation for the models with the same references. Meanwhile, the estimation yielded from spherical model is quite far from the reference 5124 K. N. Sari et al. exponential and Gaussian models, with the mean square error value reaching 713. The estimation with bootstrap method which is the same as the reference model will be faster to converge with the maximum iteration of 50. Besides, bootstrap method enables to obtain the point estimates and interval estimates of the nugget effect, sill, and range parameters.

Research paper thumbnail of The copula-based conditional tail moments for new Pareto-type distribution

2021 ASIA-PACIFIC CONFERENCE ON APPLIED MATHEMATICS AND STATISTICS

Research paper thumbnail of Estimating Copula-Based Extension of Tail Value-at-Risk and Its Application in Insurance Claim

Risks

Dependent Tail Value-at-Risk, abbreviated as DTVaR, is a copula-based extension of Tail Value-at-... more Dependent Tail Value-at-Risk, abbreviated as DTVaR, is a copula-based extension of Tail Value-at-Risk (TVaR). This risk measure is an expectation of a target loss once the loss and its associated loss are above their respective quantiles but bounded above by their respective larger quantiles. In this paper, we propose nonparametric estimators for DTVaR and establish their property of consistency. Moreover, we also propose the variability measure around this expected value truncated by the quantiles, called the Dependent Conditional Tail Variance (DCTV). We use this measure for constructing confidence intervals of the DTVaR. Both parametric and nonparametric approaches for DTVaR estimations are explored. Furthermore, we assess the performance of DTVaR estimations using a proposed backtest based on the DCTV. As for the numerical study, we take an application in the insurance claim amount.

Research paper thumbnail of Spektrum Gstar(1;1)

In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) mo... more In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) model by considering the model as VMA( ∞ ). The spectrum can be obtained by following steps: represent the model as an VMA( ∞ ) and convert the model to the backward operator form, then substitute the coefficient model to the spectrum of VMA( ∞ ) model. The procedure of finding spectrum of GSTAR(1;1) which parameters are given, is illustrated by a two dimensional GSTAR(1;1) model.

Research paper thumbnail of n-Normed Spaces with Norms of Its Quotient Spaces

Journal of Physics: Conference Series, 2018

The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characte... more The concept of n-normed spaces is a generalization of the concept of normed spaces. Some characteristics of n-normed spaces have been discussed by many researchers. These spaces are usually observed using a set of n linear independent vectors. In this paper, we will construct quotient spaces of an n-normed space with respect to n linear independent vectors. We define a norm in each quotient space by using the n-norm that we have. Norms of these quotient spaces will be a new viewpoint in observing characteristics of n-normed spaces.

Research paper thumbnail of Mechanical Properties and Microstructure at Stainless Steel HAZ from Dissimilar Metal Welding After Heat Treatment Processes

IOP Conference Series: Materials Science and Engineering, 2019

Metallurgy of HAZ at both metals after dissimilar metal welding is important to be evaluated, bec... more Metallurgy of HAZ at both metals after dissimilar metal welding is important to be evaluated, because differences in metallurgical characteristics due to heating effect on bothHAZ might take place after the process. For the case of austenitic stainless steel, metallurgical aspects that should be considered after welding are the formation of chromium carbide (sensitization) and delta ferrite phase. In the present research, focus is given on the HAZ microstructure and hardness both after welding and post-heat treatment process. Microstructure observation was carried out by optical microscope and Scanning Electron Microscope (SEM), whereas hardness testing was carried out by micro-Vickers method. From this study, it can be concluded that the increase in heat treatment temperature can reduce the volume fraction of delta ferrite and chrome carbide precipitation, whereas hardness at the HAZ region decreases after the heat treatment.

Research paper thumbnail of A formula for the g-angle between two subspaces of a normed space

Beiträge zur Algebra und Geometrie / Contributions to Algebra and Geometry, 2017

We develop the notion of g-angle between two subspaces of a normed space. In particular, we discu... more We develop the notion of g-angle between two subspaces of a normed space. In particular, we discuss the g-angle between a 1-dimensional subspace and a t-dimensional subspace for t ≥ 1 and the g-angle between a 2-dimensional subspace and a t-dimensional subspace for t ≥ 2. Moreover, we present an explicit formula for the g-angle between two subspaces of ℓ p spaces.

Research paper thumbnail of Konstruksi Interpolator Morfologi Biner 2D Dengan Metrik Hausdorfi

Dalam Matematika Morfologi, interpolasi gambar biner dipandang sebagai masalah interpolasi pada h... more Dalam Matematika Morfologi, interpolasi gambar biner dipandang sebagai masalah interpolasi pada himpunan. Misalkan X dan Y adalah himpunan-himpunan yang menyatakan dua buah gambar biner 2D, maka interpolasi dari kedua gambar biner ini akan menghasilkan deretan gambar baru yang merupakan transformasi gam- bar biner pertama (X) ke gambar biner lainnya (Y ). Metode yang digunakan dalam interpolasi ini adalah dengan menggunakan metrik Hausdorfo h(X; Y ) = max supx2X d(x; Y ); supy2Y d(y;X) . Dalam tugas akhir ini akan dikonstruksi deretan fZfig, interpolator yang membentuk geodesik dengan memodifikasi metrik Hausdorfi oleh dilasi.

Research paper thumbnail of Beberapa Aplikasi dari Ultraproducts di Dalam Teori Model

Jurnal Matematika Sains, Jul 10, 2009

Research paper thumbnail of Simulation of angle on geometry anisotropic semivariogram modeling in the case of oil in Jatibarang reservoir

AIP Conference Proceedings, 2015

Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a ... more Anisotropic semivariogram modeling can be aplied in petroleum industry where the angle between a pair of wells has important function in defining the spatial correlation between wells. In geometry anisotropic, function of range is formulated in trigonometric functions of the angle between pairs of wells that have periodicity property. The fluctuations of range will affect on shifting geometry anisotropic models with different properties for each quadrant of angle. In three semivariogram models (exponential, spherical and gaussian), the increasing of angle give difference influence for range function and the shifting of semivariogram value.

Research paper thumbnail of Spektrum Gstar(1;1)

Jurnal Matematika Sains, Dec 10, 2009

In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) mo... more In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) model by considering the model as VMA( ∞ ). The spectrum can be obtained by following steps: represent the model as an VMA( ∞ ) and convert the model to the backward operator form, then substitute the coefficient model to the spectrum of VMA( ∞ ) model. The procedure of finding spectrum of GSTAR(1;1) which parameters are given, is illustrated by a two dimensional GSTAR(1;1) model.

Research paper thumbnail of Spektrum Gstar(1;1)

Jurnal Matematika dan Sains, 2008

In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) mo... more In this paper we formulate the spectrum (spectral density matrix) of the stationary GSTAR(1;1) model by considering the model as VMA(∞). The spectrum can be obtained by following steps: represent the model as an VMA(∞) and convert the model to the backward operator form, then substitute the coefficient model to the spectrum of VMA(∞) model. The procedure of finding spectrum of GSTAR(1;1) which parameters are given, is illustrated by a two dimensional GSTAR(1;1) model.