Judul: Water Quality of River Inside and Outside the Sibual – Buali Nature Reserve Area, South Tapanuli
Abstrak: Cagar Alam (CA) Sibual – buali merupakan kawasan hutan konservasi yang berfungsi sebagai perlindungan sistem hidrologi, salah satunya yaitu aliran Sungai Aek Nabara dan Sungai Aek Sitandiang supaya tetap terjaga kualitas airnya dari kerusakan. Penggunaan lahan sempadan sungai di luar kawasan CA akan berpengaruh terhadap perubahan kualitas perairan dibawahnya. Penelitian ini bertujuan untuk mengkaji status kualitas air Sungai Aek Nabara, dan Sungai Aek Sitandiang di dalam kawasan dan perubahannya di luar kawasan Cagar Alam Sibual – buali. Penelitian dilakukan di Sungai Aek Nabara dan Sungai Aek Sitandiang. Metode pengumpulan data berupa data fisik kualitas air, pengambilan spesimen makrozoobenthos, dan data beban pencemaran. Pencemaran di dalam kawasan cagar alam lebih rendah dibandingkan dengan di luar kawasan cagar alam dan pengaruh potensi beban pencemaran Sungai Aek Nabara dan Aek Sitandiang masih relatif kecil pada masing – masing sumber pencemar. Beban pencemaran total masing – masing sungai tergolong rendah sehingga mendukung status pencemaran kedua sungai pada kategori rendah. Kata kunci: Aek Nabara, Aek Sitandiang, Cagar Alam Sibual – buali, kualitas air, The Sibual - Buali Nature Reserve (CA) is a conservation forest area that functions as a protection for the hydrological system, one of which is the Aek Nabara River and Aek Sitandiang River to maintain its water quality from damage. Use of riparian land outside the CA area will affect changes in the quality of the waters below. This study aims to assess the water quality status of the Aek Nabara River and Aek Sitandiang River in the area and its changes outside the Sibual - Buali Nature Reserve. The research was conducted in the Aek Nabara River and Aek Sitandiang River. The data collection methods are physical water data, water quality data, macrozoobenthos specimen collection, and pollution load data. Pollution inside the nature reserve area is lower than that outside the nature reserve area and the effect of the potential pollution load of the Aek Nabara and Aek Sitandiang rivers is still relatively small at each pollutant source. The total pollution load of each river is classified as low so that it supports the pollution status of the two rivers in the low category. Keywords: Aek Nabara, Aek Sitandiang, Sibual – buali nature reserve, water quality
Keyword: Aek Nabara, Aek Sitandiang, Sibual – buali nature reserve, water quality

Judul: Penetapan Indeks Mutu Air Sungai Cikeas, Sungai Cileungsi, dan Kali Bekasi Berkaitan Tata Guna Lahan
Abstrak: Penggunaan lahan pada daerah aliran Sungai Cileungsi, Cikeas, dan Kali Bekasi yang sangat beragam dapat memberikan pengaruh terhadap kualitas air di ketiga perairan tersebut. Penelitian ini bertujuan untuk menilai status mutu kualitas air sungai Cileungsi, Cikeas, dan Kali Bekasi dalam kaitannya dengan penggunaan lahan. Penelitian dilakukan di Sungai Cileungsi, Sungai Cikeas, dan Kali Bekasi dengan 11 titik lokasi pengamatan. Data spasial yang digunakan dalam penentuan tata guna lahan beserta luasnya berasal dari pengolahan citra satelit dan DEM (digital elevation model). Status kualitas air Sungai Cikeas, Cileungsi, dan Kali Bekasi dalam kategori kelas II berdasarkan metode Indeks Pencemaran dikategorikan tercemar ringan. Hasil analisis menunjukkan luasan tata guna lahan tidak berhubungan secara signifikan dengan parameter DO, BOD, COD, dan amonia kecuali parameter TSS. Kualitas air Sungai Cikeas, Sungai Cileungsi dan Kali Bekasi cenderung menurun ke arah hilir terutama pada segmen sungai yang didominasi lahan terbangun., Land use patterns in the watershed of Cileungsi, Cikeas, and Kali Bekasi Rivers might have deleterious impacts on the water quality of those rivers. In correlation to the land utilization, a study was conducted for the purpose to evaluating water quality status of Cileungsi, Cikeas, and Kali Bekasi Rivers. The study was carried out by sampling of waters at the aforementioned rivers at 11 sampling points. The spatial data used for land use patterns determination and their areas were processed from satellite image data and DEM (Digital Elevation Model). Using Pollution Index Method, the water quality status of Cileungsi, Cikeas and Kali Bekasi Rivers were classified as Category II indicating that the rivers were slightly polluted. Except for TSS, results of the analyses demonstrated that levels of DO, BOD, COD, and ammonia were not significantly correlated to land use patterns. From upstream to downstream, the water quality of Cileungsi, Cikeas, and Kali Bekasi Rivers were decreasing particularly at the river segment dominated by built-up land.
Keyword: land use, pollution index, water quality

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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