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Model Matematika Pada Mekanisme Laju Korosi Logam Baja Karbon dengan Penambahan Inhibitor Nuning Nuraini; Novriana Sumarti; Deana Wahyuningrum
Jurnal Matematika & Sains Vol 17, No 1 (2012)
Publisher : Institut Teknologi Bandung

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Korosi pada logam, yang disebabkan reaksi dengan lingkungannya, merupakan proses pelarutan logam membentuk senyawanya dalam lingkungan korosif seperti adanya air, gas oksigen dan karbondioksida.Â Korosi tidak dapat dihilangkan, namun dapat dikendalikan atau dicegah. Salah satu cara untuk mengatasi korosi, terutama yang terjadi pada permukaan bagian dalam suatu pipa logam, adalah dengan penambahan suatu inhibitor korosi.Â Dengan melihat proses terjadinya korosi dari sudut pandang berkurangnya logam persatuan waktu, diturunkanlah suatu model matematika yang memperlihatkan pengaruh senyawa inhibitor korosi terhadap logam, khususnya baja karbon dalam larutan NaCl 1%.Â Model yang diperoleh, yang merupakan pengembangan dari model sebelumnya, menggambarkan penambahan senyawa inhibitor dengan 2 cara, yaitu pada saat awal saja dan cara penambahan secara kontinu. Hasil yang didapat menunjukkan beberapa nilai konsentrasi dari inhibitor memberikan pengaruh pada mekanisme laju korosi secara efisien untuk menghentikan proses korosi. Kata kunci: Baja karbon, Inhibitor korosi, Laju korosi, Model matematika. Â Mathematical Model on Corrosion Rate Mechanism of Carbon Steel by Inhibitor Addition Abstract Corrosion is the deterioration of a material due to interaction with its environment. It is the dissolution process of metal in which metallic atoms are oxidized to form its compounds in the presence of water and gases, such as oxygen and carbon dioxide. Even though this corrosion cannot be eliminated, it can be controlled or prevented.Â One way to control corrosion, especially corrosion that occurred at the inner parts of metallic pipelines, is by addition of corrosion inhibitor. If the corrosion process was assumed as the rate of decaying process of metal per times unit, then the mathematic model can be derived to describe the effect of addition of inhibitor towards corrosion rate of metal, especially carbon steel in 1% NaCl solution. The result show that several values of inhibitor concentration provide the efficient effect on the corrosion rate mechanism to stop the corrosion process. Keywords: Carbon steel, Corrosion inhibitor, Corrosion rate, Mathematical model.

Model of Deposit and Loan of A Bank Using Spiral Optimization Algorithm Ansori, Moch Fandi; Sidarto, Kuntjoro Adji; Sumarti, Novriana
Journal of the Indonesian Mathematical Society Volume 25 Number 3 (November 2019)
Publisher : IndoMS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22342/jims.25.3.826.292-301

Nowadays, the study of financial stability of banking is important, which is to observe the behavior of the bank in the future. In this paper, a simple model of deposit and loan of a bank is solved analytically and numerically, and then it is implemented into data of four groups of commercial banks in Indonesia based on their capitals. From the data for each group of banks, the parameters will be estimated using the Spiral Optimization Algorithm. The results show that the algorithm gives satisfactory solutions in terms of closeness between the analytical and numerical solutions. In the long run, the deposit and loan volumes will be stable at their equilibrium points which showing the good condition of the future of the banks based on current state.

Model of Deposit and Loan of A Bank Using Spiral Optimization Algorithm Moch Fandi Ansori; Kuntjoro Adji Sidarto; Novriana Sumarti
Journal of the Indonesian Mathematical Society Volume 25 Number 3 (November 2019)
Publisher : IndoMS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22342/jims.25.3.826.292-301

Nowadays, the study of financial stability of banking is important, which is to observe the behavior of the bank in the future. In this paper, a simple model of deposit and loan of a bank is solved analytically and numerically, and then it is implemented into data of four groups of commercial banks in Indonesia based on their capitals. From the data for each group of banks, the parameters will be estimated using the Spiral Optimization Algorithm. The results show that the algorithm gives satisfactory solutions in terms of closeness between the analytical and numerical solutions. In the long run, the deposit and loan volumes will be stable at their equilibrium points which showing the good condition of the future of the banks based on current state.

Some Problems on the Making of Mathematical Modelling of a Profit-Loss Sharing Scheme Using Data Simulation Novriana Sumarti; Kuntjoro Adji Sidarto; Muhammad Syamsuddin; Vina Fitriyani Mardiyyah; Abu Rizal
Journal of Mathematical and Fundamental Sciences Vol. 47 No. 1 (2015)
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.2015.47.1.1

The mathematical model for a profit-loss sharing scheme is formulated in order to see how this scheme can replace the traditional practice of lending money against high interest by usurers. It is sourced from the musyarakah method in Islamic Syariah law and implemented for small-scale investments of traditional-market traders. They are the common target of usurers, so they may end up poorer than they were before. The main goal of the model is to find the appropriate portion of profit share, so the investment is profitable not only for the investor but also for the trader. There are three main problems in the process of formulating the mathematical model and finding optimized results. The first problem is providing the appropriate amount of data to be implemented in the model. The second problem is determining the objective function for the optimization of the portion of profit share. The last problem is determining the appropriate values of the parameters for certain types of traders. We found a significant result in determining the appropriate values of the parameters that explain the potential capability of the traders in handling larger amounts of capital to be invested in order to achieve our main goal.

A MATHEMATICAL MODEL OF PROFIT-LOSS SHARING SCHEME OF SMALL INVESTMENT FOR TRADITIONAL MARKET TRADERS USING THE SEMI-FUZZY LOGIC APPROACH Sumarti, Novriana; Marendri, Adythia Dean
Journal of Islamic Monetary Economics and Finance Vol 2 No 2 (2017)
Publisher : Bank Indonesia

A mathematical model of micro-finance investment using profit-loss sharing scheme are made and implemented to simulated data. Here profits from the venture will be shared in a portion between the investor and the entity running the business. The scheme can be classified as Musharaka type of investment in Sharia economy. The proposed model is theoretically implemented with data from small-scale traders at a local traditional market who have small turnover. They are common target of usurers who lend money with high interest rate and penalties. If the traders are in unfortunate conditions, they are potentially in poorer condition than before committing themselves to the usurer. In the conventional practices of the profit sharing scheme, the investor will get a fixed portion of the trader’s income, which is applied for all kind of small-scale traders. If the traders are diligent and hard worker and have very high turnover, then the investor will gain much more profit whether the contributed capital is small or large. In this paper, the scheme is implemented using Semi-Fuzzy Logic Approach so that the profit-loss sharing scheme can achieve its intended goal, which is to make a profitable investment not only for the investor but also for traders. The approach is not fully using Fuzzy Logic because some variables are still in crisp numbers and the optimization problem is regular in the form of crisp numbers. Based on the existing data, the results show that the optimal profit share is depended on the income of the traders. The higher the income coming from the venture, the lesser the profit share for the investor which is reasonable with the fixed initial contributed capital.

Observation of Calculated Lapse Rate for Sharia Life Insurance Data : A Study Case Andaria, Rini; Sumarti, Novriana; Puspita, Dila
Jambura Journal of Mathematics Vol 7, No 1: February 2025
Publisher : Department of Mathematics, Universitas Negeri Gorontalo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37905/jjom.v7i1.30587

Modeling a lapse rate is an important subject for life insurance companies because a lapse rate can impact the premium pricing, the reserves, and profitability. In this paper, we calculate the lapse rate and implement a similar approach proposed by the Life Insurance Marketing and Research Association (LIMRA) and the Society of Actuaries (SOA). We analyze lapse rate data from one Sharia insurance company in Indonesia, covering an eight-year period with a total of more than one hundred thousand policyholders. Sharia insurance is aimed at managing contributions based on Sharia principles for mutual assistance and protection by providing compensation to participants/policyholders for losses due to an uncertain event or by providing payments based on the death or the survival of participants. We observe the lapse rates by the face amount group, by genders, and by premium payment frequencies. We found three conclusions, which are mostly that the lower the face amount group, the higher the lapse rate; the lapse rate is not significantly different by gender; and the lapse rate for quarterly payment frequency is higher than for other frequencies.

A MATHEMATICAL MODEL OF PROFIT-LOSS SHARING SCHEME OF SMALL INVESTMENT FOR TRADITIONAL MARKET TRADERS USING THE SEMI-FUZZY LOGIC APPROACH Sumarti, Novriana; Marendri, Adythia Dean
Journal of Islamic Monetary Economics and Finance Vol. 2 No. 2 (2017)
Publisher : Bank Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21098/jimf.v2i2.650

A mathematical model of micro-finance investment using profit-loss sharing scheme are made and implemented to simulated data. Here profits from the venture will be shared in a portion between the investor and the entity running the business. The scheme can be classified as Musharaka type of investment in Sharia economy. The proposed model is theoretically implemented with data from small-scale traders at a local traditional market who have small turnover. They are common target of usurers who lend money with high interest rate and penalties. If the traders are in unfortunate conditions, they are potentially in poorer condition than before committing themselves to the usurer. In the conventional practices of the profit sharing scheme, the investor will get a fixed portion of the trader’s income, which is applied for all kind of small-scale traders. If the traders are diligent and hard worker and have very high turnover, then the investor will gain much more profit whether the contributed capital is small or large. In this paper, the scheme is implemented using Semi-Fuzzy Logic Approach so that the profit-loss sharing scheme can achieve its intended goal, which is to make a profitable investment not only for the investor but also for traders. The approach is not fully using Fuzzy Logic because some variables are still in crisp numbers and the optimization problem is regular in the form of crisp numbers. Based on the existing data, the results show that the optimal profit share is depended on the income of the traders. The higher the income coming from the venture, the lesser the profit share for the investor which is reasonable with the fixed initial contributed capital.

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