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Journal of Mathematical and Fundamental Sciences
Published by Institut Teknologi Bandung
ISSN : 23375760     EISSN : 23385510     DOI : https://doi.org/10.5614/j.math.fund.sci.
Core Subject : Science, Education,
Astronomy Chemistry Earth & Planetary Sciences Mathematics Physics
Journal of Mathematical and Fundamental Sciences welcomes full research articles in the area of Mathematics and Natural Sciences from the following subject areas: Astronomy, Chemistry, Earth Sciences (Geodesy, Geology, Geophysics, Oceanography, Meteorology), Life Sciences (Agriculture, Biochemistry, Biology, Health, Medical, Pharmacy), Mathematics, Physics, and Statistics.
Arjuna Subject : Matematika - Matematika (Lain-Lain)
Articles 689 Documents
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SEM-EDX Analysis of Laser Surface Alloying on Aluminum Noriah Bidin; Mundzir Abdullah; Mohd Syafik Shaharin; Yusef Abdul Alwafi; Dwi Gustiono Riban; Moh Yasin
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 1 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.1.5

Abstract

Microstructure and chemical composition changes on the alloyed aluminum surface were investigated using SEM-EDX analysis. A Q-switched Nd:YAg laser was focused to induce breakdown and plasma formation. The high plasma temperature and the shock wave pressure were responsible for speeding up the laser surface alloying process. The rapid heat and cooling process introduced a non-equilibrium condition causing changes in the microstructure as well as the chemical composition of the alloyed aluminum surface. The remelted layer and molten pools were realized after the aluminum received a power density greater than 5 x 108 Wcm-2. The chemical composition change confirms that the convection process had taken place during the alloying process.
A Note on Strongly Lower Semi-Continuous Functions and the Induced Fuzzy Topological Space Generated by Them Apu Kumar Saha; Debasish Bhattacharya
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 1 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.1.6

Abstract

A new class of functions called strongly lower semi-continuous (SLSC) functions is defined and its properties are studied. It is shown that the arbitrary supremum and finite infimum of SLSC functions are again SLSC. Using these functions, an induced fuzzy topological space, called s-induced fuzzy topological space on a topological space (X, T), is introduced. Moreover, some incorrect results on fuzzy topological spaces obtained previously by some authors are identified and modified accordingly. Examples of the newly defined induced space are given and their various properties are investigated. Interrelationships between a fuzzy topological space (X, F) and the s-induced fuzzy topological space generated by the crisp members of F are examined. In this process, different lower semi-continuities and induced fuzzy spaces generated by them have been defined in a general set up and their few properties have been studied.
g- Inverses of Interval Valued Fuzzy Matrices Arunachalam R. Meenakshi; Muniasamy Kaliraja
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 1 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.1.7

Abstract

In this paper, we have discussed the g-Inverses of Interval Valued Fuzzy Matrices (IVFM) as a generalization of g- inverses of regular fuzzy matrices. The existence and construction of g-inverses, {1, 2} inverses, {1, 3} inverses and {1, 4} inverses of Interval valued fuzzy matrix are determined in terms of the row and column spaces.
Development of an Inversion Method for Low Velocity Medium A. Afnimar; Andri Dian Nugraha; Ahmad Syahputra
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 1 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.1.8

Abstract

The main problem with the inversion of a low velocity medium is the application of an appropriate ray tracing method after choosing a suitable model parameterization. Block parameterization is not suitable, because it is not capable of representing the velocity model well. A large amount of blocks with a small grid size are needed to express the model well, but in that case, a ray coverage problem will be encountered. A knot-point parameterization model is better suited than a block model, because it can express the velocity model well, while the number of variables is much smaller. Ray calculation using the pseudo-bending method is not appropriate for the velocity model because of an instability problem at high velocity gradients. The crucial problem of this method involves the initial ray-path that is optimized in order to obtain the "true" ray, but does not satisfy the Fermat principle. These problems can be solved by applying the eikonal-solver method, because this can handle high-velocity gradients and does not need an initial ray path. Using a suitable model parameterization and appropriate ray tracing method, the inversion can obtain good results that fit the desired output. Applying a block model and the pseudo-bending method will not produce the desired output.
Correlation and Relativistic Effects on the Level Structure of Negative Ions of Atoms with Half-filled p Shell Gülay Günday Konan; Leyla Özdemir; Nurgül Gündüz Atik
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.1

Abstract

The level structure for negative ions (anions) of some atoms with half-filled p shell have been investigated using the multiconfiguration Hartree-Fock method with Breit-Pauli relativistic effects (MCHF+BP method). Thus, we have performed a systematic calculation including correlation and relativistic corrections for negative ions of these atomic systems. Investigations into the level structures of negative ions provide valuable insight into the fundamental problem of many-body motion. The correlation and relativistic effects in negative ions relative to neutral atoms and positive ions are greatly expected. In this work, we also discuss calculations for these effects in view of the MCHF+BP method.
Hawking Temperature of the Reissner-Nordstrom-Vaidya Black Hole T. Triyanta; Anike N. Bowaire
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.2

Abstract

We have derived the Hawking temperature of the Reissner-Nordstrom-Vaidya black hole by the use of both the radial null geodesic and the complex path methods. We have obtained that the mass dependence of the temperature in the Reissner-Nordstrom-Vaidya black hole is not as simple as that in the Schwarzschild black hole, but still we regain the conclusion, as in the case of the Schwarzschild black hole, that a higher Hawking temperature corresponds to a lower mass of a black hole.
Optimization Models for the Control of Saltwater Intrusion Robert Willis
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.3

Abstract

A general optimal control model was developed for the control of saltwater intrusion in coastal aquifer systems. The underlying sharp-interface and density-dependent hydraulic and water quality response equations are presented. Different solution algorithms are described for the control problem, including the imbedding method, Box's algorithms, and the linked simulation-optimization methodology (LSO). Several field applications are presented. The optimization approach, despite requiring significant computation resources, is superior to conventional simulation methods. Optimization produces not only locally optimal planning, design, and operational policies, but also tradeoffs associated with environmental and hydraulic objectives.
Estimating Oil Reservoir Permeability and Porosity from Two Interacting Wells S. Sutawanir; Agus Yodi Gunawan; Nina Fitriyati; Iskandar Fahmi; Anggita Septiani; Rini Marwati
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.4

Abstract

The Ensemble Kalman Filter (EnKF) can be used as a method to estimate reservoir parameters, such as permeability and porosity. These parameters play an important role in characterizing reservoir performance. The EnKF is a sequential estimation method that uses the parameters at t "“ 1 (called prior) to estimate the parameters at t adjusted by observations at t (called posterior). In this paper, the EnKF was used to estimate the reservoir parameters for the case of a linear flow of two interacting production-injection oil wells. The Laplace transform was used to obtain an analytical solution of the diffusivity equation. A state space representation was generated using the analytical solution. A simulation study showed that the proposed method can be used successfully to estimate the reservoir parameters using well-pressure observations.
New Results on the Existence of Periodic Solutions for Rayleigh Equation with State-Dependent Delay Cemil Tunç
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.5

Abstract

We give certain sufficient conditions for the existence of periodic solutions to a Rayleigh-type equation with state-dependent delay. With this work we extend and improve some known results in the literature.
Total Edge Irregularity Strength of the Disjoint Union of Helm Graphs Muhammad Kamran Siddiqui; N. Nurdin; Edy Tri Baskoro
Journal of Mathematical and Fundamental Sciences Vol. 45 No. 2 (2013)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2013.45.2.6

Abstract

The total edge irregular k-labeling of a graph G=(V,E) is the labeling of vertices and edges of G in such a way that for any different edges their weights are distinct. The total edge irregularity strength, tes (G), is defined as the minimum k for which G has a total edge irregular k-labeling. In this paper, we consider the total edge irregularity strength of the disjoint union of m special types of helm graphs.

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