Judul: IPB (Bogor Agricultural University)
Abstrak: Saringan media campuran dengan mempergunakan kombinasi 4 dan 5 jenis bahan penyaring seperti ijuk setebal 5 cm, dan kerikil, bata merah, zeolit dan pasir masing-masing setebal 4 cm. Semua bahan penyaring dimasukkan ke dalam tong plastik berukuran tinggi 40 cm, dan berdiameter 18 cm, dengan posisi ijuk diatas dan di bawah lapisan kerikil, bata merah, zeolit dan pasir, diuji coba bada penelitian lapang skala kecil di Jakarta utara, mulai dari juni 2003 sampai dengan Juli 2004. Air yang disaring di ambil dari air kali Sunter yang tercemar. Semua bahan penyaring di cuci sebelum dipergunakan. Penilaian baku mutu air berdasarkan SK Gubernur DKI Jakarta.
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Judul: IPB (Bogor Agricultural University)
Abstrak: Tujuan penelitian adalah untuk mengetahui kemampuan dan keefektifan penyaringan air Sungai Ciliwung terhadap beberapa sifat fisik dan kimia air dengan bahan penyaring pasir, ijuk, arang dan campuran pasir-ijuk, pasirarang, arang-ijuk, dan pasir-ijuk-arang. Contoh air diambil dari Sungai Ciliwung di lokasi Gadog, Bogor dan Jakarta. Hasil penyaringan dilihat peranannya untuk kebutuhan air minum baku.
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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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