Judul: Pencirian Bioplastik Komposit Tepung Singkong dan Natrium Alginat dengan Aditif Limonena Kulit Jeruk
Abstrak: Bioplastic made from plasticized glycerol cassava flour with the addition of sodium alginate and limonene orange peel is an alternative to solve the problem of plastics waste. Bioplastic was produced by adjusting the composition of cassava flour:glycerol:sodium alginate:limonene orange peel as much as 75:5:16:4, 75:5:12:8, 75:5:8:12, 75:5:4:16, and 75:5:0:20. The analysis was performed to measure density, tensile strength, percent elongation, water vapor permeability, thermal properties, morphology, and functional groups. The value of density and tensile strength of bioplastics decreased with the addition of limonene orange peel, but the value of percent elongation increased significantly that means the elasticity of bioplastic is better. Functional groups analysis showed that bioplastics formed through physic interaction. Hydrophobic characteristic of limonene could decreased water vapor permeability of bioplastics and plasticizers characteristic of limonene that could entered into the polymer building blocks made bioplastics more brighter, elastic, and homogeneous.
Keyword: Sodium alginate., Limonene, Cassava, Bioplastic

Judul: Bioplastic composite of tapioca starch plastisized with sorbitol, sodium alginate and limonene
Abstrak: Bioplastik dapat dibuat dari bahan dasar pati dan protein. Bioplastik berbahan dasar pati memiliki keuntungan, yaitu harga yang relatif murah dan mudah didapat dibandingkan protein. Akan tetapi, bioplastik berbahan dasar pati lebih rapuh, sehingga diperlukan bahan tambahan untuk mengatasi kerapuhan. Tujuan penelitian ini adalah membuat dan mencirikan bioplastik komposit dari pati tapioka terplastisasi sorbitol, natrium alginat, dan limonena berdasarkan perbedaan komposisinya. Bioplastik dengan tambahan limonena 2.5% memiliki nilai elongasi, kuat tarik, dan bobot jenis yang lebih tinggi dibandingkan bioplastik dengan tambahan limonena 5.0%, 7.5%, dan 10.0%. Penambahan limonena juga menurunkan nilai permeabilitas uap air. Bioplastik dengan komposisi natrium alginat:limonena:sorbitol (10.0:2.5:7.5) lebih stabil terhadap panas yang ditunjukkan dengan suhu leleh lebih tinggi dibandingkan bioplastik dengan komposisi (7.5:2.5:10.0). Pada analisis morfologi, komponen penyusun bioplastik dengan komposisi (7.5:2.5:10.0) terdistribusi merata pada matriks bioplastik yang didukung dengan terdapatnya puncak suhu leleh tunggal pada termogram., Bioplastic can be made of different sources such as starches and proteins. The benefits of bioplastic starch-based are relatively low cost and easily obtained. The disadvantage of starch-based bioplastic is brittle. In this experiment, sodium alginate, limonene and sorbitol were added to overcome that problem. The objectives of this study are to synthesis and characterize the bioplastic made of tapioca starch plastisized with sorbitol, sodium alginate and limonene based on the various compositions. The addition of limonene 2.5% result in highest elongation, tensile strength, and density as compared to compositions (5.0%, 7.5%, and 10.0%). The addition limonene also decreased water vapour permeability. Bioplastic composition of sodium alginate:limonene:sorbitol (10.0:2.5:7.5) has more heat stability than that of the composition of (7.5:2.5:10.0) which showing a higher melting point. Morphology analysis showed that the bioplastic composition of (7.5:2.5:10.0) distributed evenly on the matrix of bioplastics as supported by a single melting point peak on the thermogram. Keywords: bioplastic, limonene, sodium alginate, sorbitol, starch
Keyword: bioplastik, limonena, natrium alginat, pati, sorbitol

Judul: The Effects of Variance of Interest rate to Variance of Annuity Future Values
Abstrak: Time value of money is a concept that refers to the difference of the value of money due to time difference. The value of money for present time would not be the same as the value of money in the future. The value of money for present time is called as Present Value (PV) of the money and the value of money for future time is called Future Value (FV) of the money. Determination the value of money, for present and future time, depends on the time and rate of return. The value of money is determined by several factors such as inflation, fluctuation of interest rates, and government policy in securities and taxation. Due to fluctuation of the value of money we need a FV formulation, it is useful for knowing whether an investment can be profitable or not, and this information is useful also in budget analysis. Annuity is defined as a series of payments made for a specific period. The payment, fixed or varied, can be made at the beginning or at the end of the period. Annuity paid at the beginning of the period is called annuity-due and annuity paid at the end of the period is called immediate annuity-certain. The accumulated value of the annuity after few years later is called as a final value or a future value. Burnecki et al. (2003) have discussed about the FV of a fixed-rate annuity in which payments are made according to the arithmetic or geometric series. They have also examined FV for annuities in which payments are made according to arithmetic or geometric series with random rates of interest. This paper examines FV for annuity-due in which payments are made according to arithmetic or geometric series with interest rates as a random variable, which is normal distribution ,  . Future value formula is expressed in recursive form. FV for annuity-due which payments are made according to the arithmetic or geometric series with random rates of interest is calculated by theoretical way and simulation way. The random rates of interest is denoted as k k i  i  , where k i an independent random variable; i is a constant and k  is a random variable which has normal distribution ,  . By using the determined parameters, a sequence of random rates of interest are generated for theoretical calculation. Meanwhile for the simulation, the random rates of interest is generated 1000 times for the simulation. The generated data give mean value, variance, and standard deviation. Moreover, error of mean value, variance, and standard deviation from the theoretical and simulation results are calculated. Error calculation uses Symmetric Mean Absolute Percentage Error (SMAPE). The smaller the value of SMAPE is the more accurate the simulation. The interest rate variances are varied from 0.000036 to 0.0001 to study the relationship between variance of rates of interest and variance of future value. The theoretical and simulation results show that when the variance of random rates of interest increases, then the variance of FV increases linearly. FV of the annuity-due in
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