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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 695 Documents
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On Effective Locations of Catalytic Active Sites in Phase Boundary Catalysts Hadi Nur; Nur Hidayah Mohd Ran; Nursyafreena Attan; Shigeru Ikeda; Bunsho Ohtani
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 2 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.2.5

Abstract

Zeolite loaded with alkylsilane-covered titanium oxide was found to be more effective than its nonporous silica counterpart as phase-boundary catalyst (PBC) to promote epoxidation of alkenes with aqueous hydrogen peroxide. It was demonstrated that the phase-boundary catalyst system required neither stirring to make an emulsion, nor addition of a cosolvent to make a homogeneous solution to drive the reaction. However, some basic facts about them remain unclear, such as the question as to where an effective location of the active sites of PBC resides: is it on the external surface of the catalysts, or in their pores? In order to elucidate this problem, TS-1, HZSM-5 and zeolite loaded with alkylsilane"“covered sulfonic acid in which the location of the active sites is mainly inside the pore system, were chosen as model catalysts. Catalytic activities of the catalysts TS-1 and HZSM-5 were examined after modification with n-octadecyltrichlorosilane (ODS). Their activities were compared with zeolite loaded with alkysilane-covered titanium oxide particles, in which the active sites are on the external surface in reactions of 1-octene with aqueous H2O2 and cyclohexene with water as model reactions. The study suggests that the location of the active sites on the external surface plays an important role in the phenomenon of phase-boundary catalysis.
An Asymptotic Study of the Steady State Model of Oxygen Diffusion in Tissue Regions Kartika Yulianti; Agus Y. Gunawan
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 2 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.2.6

Abstract

Oxygen plays an important role in the metabolism of cells inside the human body. The transfer of oxygen from blood to tissue takes place in capillaries through a diffusion process. The capillary-tissue region is usually represented by the so-called Krogh cylinder model, in which the distribution of the oxygen concentration in a tissue region leads to a diffusion equation with oxygen consumption rates following the Michaelis-Menten kinetics. In this paper, we restrict ourselves to the steady state case and solve the equation analytically by means of asymptotic expansion for a particular limit of the oxygen consumption rate. Results show that there exists a critical ratio between supply and consumption of oxygen in the tissue region in order to fulfill the cell's oxygen requirements. Above from this critical ratio, we also found a critical distance in the tissue region above which the oxygen concentration vanishes. We compared our asymptotic results with numerical simulations, which turned out to be quite in agreement.
A New Procedure for Generalized STAR Modeling using IAcM Approach Utriweni Mukhaiyar; Udjianna S. Pasaribu
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 2 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.2.7

Abstract

A new procedure of space-time modeling through the Invers of Autocovariance Matrix (IAcM) is proposed. By evaluating the IAcM behaviors on behalf of the Generalized Space-Time Autoregressive (GSTAR) process stationarity, we may find an appropriate model to space-time data series. This method can complete the Space-Time ACF and PACF methods for identifying space-time models. For study case, we apply the GSTAR models to the monthly tea production of some plantations in West Java, Indonesia.
Hydrothermal Preparation of Apatite-Type Phases La9.33Si6O26 and La9M1Si6O26.5 (M = Ca, Sr, Ba) Atiek Rostika Noviyanti; Bambang Prijamboedi; I Nyoman Marsih; Ismunandar Ismu
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 2 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.2.8

Abstract

Apatite-type lanthanum silicates show a great potential to be used as an electrolyte for intermediate- to low-temperature (600-700 ï‚°C) solid oxide fuel cells (ITSOFC). However, so far these materials need to be prepared using a very high-temperature method, thus there is a growing interest to prepare apatites at lower temperatures. This paper reports the synthesis of undoped La9.33Si6O26 and doped apatites (La9CaSi6O26,5, La9SrSi6O26,5, and La9BaSi6O26,5) from raw materials La2O3, Na2SiO4, BaCO3, CaCO3, and SrCO3 using a hydrothermal method. The polycrystalline apatites were obtained as a white powder, after the basic solution of the reagent mixture was heated at 240 ï‚°C in an autoclave for 3 days. Le Bail refinement of the X-ray powder diffraction data showed that the compounds have a hexagonal cell (P 63/m space group). In this paper, the undoped La9.33Si6O26 and La-doped apatite ionic conductivities are also presented.
Boolean Algebra of C-Algebras Guddati C. Rao; Perumali Sundarayya
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 3 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.3.1

Abstract

A C- algebra is the algebraic form of the 3-valued conditional logic, which was introduced by F. Guzman and C.C. Squier in 1990. In this paper, some equivalent conditions for a C- algebra to become a boolean algebra in terms of congruences are given. It is proved that the set of all central elements B(A) is isomorphic to the Boolean algebra S(A) B of all C-algebras Sa, where a  B(A). It is also proved that B(A) is isomorphic to the Boolean algebra R(A) B of all C-algebras Aa, where a B(A).
A Note on Prediction with Misspecified Models Kreshna Syuhada
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 3 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.3.2

Abstract

Suppose that a time series model is fitted. It is likely that the fitted model is not the true model. In other words, the model has been misspecified. In this paper, we consider the prediction interval problem in the case of a misspecified first-order autoregressive or AR(1) model. We have calculated the coverage probability of an upper one-step-ahead prediction interval for both properly specified and misspecified models through Monte Carlo simulation. It was found that dealing with prediction interval for misspecified model is complicated: the distribution of a future observation conditional on the last observation and the parameter estimator is not identical to the distribution of this future observation conditional on the last observation alone.
Magnetic States of the Co-ions in Ca and Y Doped (Bi,Pb)2Sr2Co2O8 Thermoelectric Materials Inge M. Sutjahja; A. A. Nugroho
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 3 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.3.3

Abstract

The magnetic states of Cobalt ions in magnetic thermoelectric materials of Bi1.5Pb0.5Ca2-zYzCo2O8 (z = 0, 0.1, 0.2, and 0.3) have been studied from the structural (X-ray diffraction) and magnetic susceptibility data. The misfit structure was revealed from refinement of the XRD data, with reduction of the lattice parameters while increasing the Y doping content. Compared with the (Bi,Pb)2Sr2Co2O8 parent compound system, the lattice parameter c was reduced significantly, while the misfit degree remained almost the same. The analysis of the magnetic data shows that the Cobalt ions are coupled antiferromagnetically within the CoO2 layers, with the existence of mixed valence states between Co3+ and Co4+ ions. Besides that, the effective magnetic moments of Cobalt ions are almost constant along the Y doping content. Assuming the orbital quenching as commonly found in most transition metal ions, the data are best fitted by taking the low-spin state of Co3+ ions and intermediate spin state of Co4+ ions. We argue qualitatively, that the spin-state transition across the gap are induced by the shrinkage of the charge transfer energy gaps between O 2p and Co g e levels due to reduction of the ionic spaces between Co and O ions.
Instability of Non-Linear Functional Differential Equations of Fifth Order Cemil Tunc
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 3 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.3.4

Abstract

In this paper, we study the instability properties of solutions of a kind of functional differential equations of the fifth order with constant delay. Using the Lyapunov-Krasovskii functional approach, we obtain certain sufficient conditions to guarantee that the zero solution of the equation is unstable.
Phase Transformation of Rice Husk Ash in the Synthesis of ZSM-5 without Organic Template Didik Prasetyoko; Neneng Ayunanda; Hamzah Fansuri; Djoko Hartanto; Zainab Ramli
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 3 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.3.5

Abstract

Phase transformation of rice husk ash in the synthesis of ZSM-5 without organic template at various crystallization times has been studied. Zeolite has been synthesized using the hydrothermal method at 175 °C with molar ratio 10Na2O : 100SiO2 : 2Al2O3 : 1800H2O with addition of silicalite-1 as seed. Solids were characterized using X-ray diffraction (XRD), infrared (IR) spectroscopy and scanning electron microscopy (SEM) techniques. Analysis of the results of XRD and IR spectroscopy indicated that ZSM-5 crystalstarted to form at 12 h of crystallization time, reaching high crystallinity after 24 h. With a crystallization time of more than 48 h, the ZSM-5 crystals had completely transformed into more stable quartz phase. Results indicated that phase transformation has occurred, in which an amorphous phase of rice husk ash has been transformed to ZSM-5 crystal phase during the early crystallization stage and continued to transform to disordered α-cristobalite phase and lastly quartz phases. SEM showed that the morphology of the ZSM-5 crystal was of an irregular hexagonal shape with particle size distribution around 3-7 μm.
Ring-Opening of Oxiranes using Taeniolite-Supported Tris(β-Diketonato)Zirconium Yessi Permana; Nobuyuki Ichikuni; Shogo Shimazu
Journal of Mathematical and Fundamental Sciences Vol. 44 No. 3 (2012)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.sci.2012.44.3.6

Abstract

A series of tris(β-diketonato)zirconium(IV) complexes was immobilized into a synthetic clay structure of Taeniolite by an ion-exchange method to generate organic/inorganic hybrid compounds. The hybrid compound served as a good catalyst for ring-opening reactions of methyl, ethyl, and dimethyl oxiranes with various alcohols to generate primary alkoxy alcohols in appreciable selectivity. This method describes a technique to immobilize cationic zirconium complexes without losing selectivity.

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