Judul: Spatial and Temporal Distribution of Dissolved Oxygen  and Nutrients in the Ciliwung River, DKI Jakarta
Abstrak: Masukan limbah organik dan anorganik dari kegiatan antropogenik di sekitar sungai berpotensi menyebabkan penurunan kualitas perairan dan pengayaan nutrien. Penelitian ini bertujuan menganalisis dan mendeskripsikan sebaran oksigen terlarut dan nutrien (amonia, nitrit, nitrat, nitrogen total, dan fosfat total) di Sungai Ciliwung, DKI Jakarta, secara spasial dan temporal. Pemantauan kualitas air dilakukan pada bulan Februari-September 2021 dari 18 stasiun pengamatan. Secara spasial, kandungan oksigen Sungai Ciliwung tergolong rendah di Jakarta Pusat dan Jakarta Utara, kandungan nitrogen total, nitrat, dan fosfat total memenuhi baku mutu di seluruh wilayah sungai, sementara kandungan amonia dan nitrit cenderung tinggi dan tidak memenuhi baku mutu di seluruh wilayah Sungai Ciliwung, DKI Jakarta. Secara temporal, konsentrasi oksigen terlarut, nitrit, nitrogen total, dan fosfat total cenderung tidak berbeda antarmusim, sedangkan konsentrasi amonia lebih tinggi di musim kemarau dan nitrat lebih tinggi di musim hujan. Status kualitas air Sungai Ciliwung, DKI Jakarta, berada pada kondisi tercemar sedang hingga berat., The input of organic and inorganic waste from anthropogenic activities around the river causes a decrease in water quality and nutrient enrichment. This study aims to analyze and describe the distribution of dissolved oxygen and nutrients (ammonia, nitrite, nitrate, total nitrogen, and total phosphate) in the Ciliwung River, DKI Jakarta, spatially and temporally. Water quality monitoring was carried out in February-September 2021 from 18 observation stations. Spatially, the oxygen content of the Ciliwung River is low in Central Jakarta and North Jakarta, the total nitrogen, nitrate, and total phosphate content meets the quality standards in the entire river area, while the ammonia and nitrite content tend to be high and do not meet the quality standards in the entire Ciliwung River area, DKI Jakarta. Temporally, concentrations of dissolved oxygen, nitrite, total nitrogen, and total phosphate tended not to differ between seasons, while ammonia concentrations were higher in the dry season and nitrate was higher in the rainy season. The water quality status of the Ciliwung River, DKI Jakarta, is in moderate to extremely polluted condition.
Keyword: dissolved oxygen, nutrients, river, spatial, temporal

Judul: Analisis Sebaran Oksigen Terlarut dengan Model Steeter-Phelps di Sungai Ciliwung.
Abstrak: DAS Ciliwung mencangkup areal mulai dari bagian hulu di Tugu Puncak Bogor sampai hilir di Teluk Jakarta. Tujuan dari penelitian ini yaitu menganalisis kualitas air, menerapkan permodelan Streeter-Phelps terhadap penurunan kandungan oksigen terlarut dan menganalisis kemampuan purifikasi alami. Lokasi mewakili kondisi dan aktivitas dari lingkungan sekitarnya dan dianggap di segmen hulu, tengah dan hilir. Hasil penelitian dapat diketahui Kualitas air Sungai Ciliwung berdasarkan metode indeks pencemaran Sungai Ciliwung termasuk tercemar ringan sampai sedang. Persamaan yang dikembangkan oleh Baecheler dan Lazo (1999) dapat menghasilkan model yang akurat dengan nilai koefisien determinasi sebesar 0.887 dan RMSE (root mean square determination) sebesar 0.114. Hal tersebut terjadi karena adanya kesesuaian beberapa karakteristik antara Sungai Ciliwung dengan Sungai Atuwara di Nigeria. Sungai Ciliwung memiliki kemampuan pemurnian dengan nilai rasio sebesar 13.85 dan 2.62 pada 2 pos bagian hulu, sedangkan pada segmen aliran selanjutnya tidak dapat melakukan pemurnian alami.
Keyword: Ciliwung, oksigen terlarut, purifikasi alami, Streeter-Phelps

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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