Judul: Effect of Land Use and Rainfall on Water Quality of the Cimandiri River, Sukabumi, Indonesia
Abstrak: Penurunan kualitas air di Sungai Cimandiri merupakan isu penting yang perlu diidentifikasi penyebabnya. Penggunaan lahan dan curah hujan di Daerah Aliran Sungai (DAS) diduga mempengaruhi kualitas air sungai. Penelitian bertujuan mengidentifikasi dampak penggunaan lahan dan curah hujan terhadap kualitas air Sungai Cimandiri. Metode penelitian dibuat menggunakan model regresi linear berganda (RLB) dan linear mixed method (LMM). Proporsi penggunaan lahan dan rata-rata curah hujan harian sebagai variabel bebas dan parameter kualitas air sebagai variabel terikat. Data penggunaan lahan, curah hujan, dan kualitas air yang digunakan adalah data periode 2017–2023. Parameter kualitas air yang digunakan, meliputi; total suspended solid (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), fosfat, dan fecal coliform. Hasil penelitian menunjukkan bahwa penggunaan lahan dan curah hujan memiliki hubungan terhadap parameter kualitas air. Penggunaan lahan memiliki pengaruh nyata (p < 0,05) terhadap parameter kualitas air, sedangkan curah hujan tidak berpengaruh nyata (p > 0,05) terhadap kualitas air secara statistik. Model regresi linear berganda untuk setiap segmen DAS memiliki kekuatan model yang bervariasi. Segmen tengah memiliki kekuatan model yang lebih baik dalam menjelaskan hubungan penggunaan lahan dan curah hujan terhadap parameter kualitas air dibandingkan segmen lain dengan nilai R2adj berkisar antara 51,32–96,05%. Linear mixed method mampu menjelaskan pengaruh segmen pada model hubungan seluruh DAS Cimandiri untuk parameter TSS (95,45%) dan DO (42,28%)., Water quality decreased in the Cimandiri River has become an important issue that requires identification of its root causes. Land use and rainfall patterns within the watershed (DAS) are presumed to influence river water quality. This study aims to identify the impacts of land use and rainfall on water quality in the Cimandiri River. The study methodology utilized multiple linear regression (MLR) and linear mixed model (LMM). The proportion of land use and average daily rainfall were utilized as independent variables, while water quality parameters served as dependent variables. The study utilized land use, rainfall, and water quality data from the period of 2017–2023. The water quality parameters assessed include total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), phosphate, and fecal coliform. The study findings indicate a correlation between land use and rainfall patterns and water quality parameters. Land use had a significant effect (p < 0.05) on water quality parameters, while rainfall did not have a statistically significant (p > 0.05) effect on water quality. The strength of the multiple linear regression models varied across watershed segments. The middle segment exhibited a better model fit in explaining the relationship between land use and rainfall with water quality parameters compared to other segments, with R2 adj values ranging from 51.32–96.05%. The linear mixed method effectively explained the influence of segments on the relationship model for the entire Cimandiri watershed for TSS (95.45%) and DO (42.28%) parameters
Keyword: Kualitas air sungai, Model campuran linear, Regresi linear berganda, linear mixed methods, multiple linear regression, water river 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
Keyword: