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: Pengaruh Perubahan Tutupan Lahan dan Pemanfaatan Sumberdaya Air terhadap Kualitas Air Sungai di Daerah Aliran Sungai Cisadane Segmen Hulu
Abstrak: Increasing the number of residents in the Cisadane watershed area upstream segment cause high river water use and land cover changes. This negative impact on the incidence of pollution load and the source of pollutants/waste that may affect the water quality of rivers and indirectly affect the level of river water pollution. The water quality is very depend on the effort to meet the needs of water for each utility. Therefore, research on the effects of land cover change and water resources utilization of river water quality in the Cisadane watershed upstream segment needs to be done. This research was conducted in the Cisadane watershed area upstream from June to August 2009. Equipments used, such as water quality data, land cover, population, utilization of river water, debit, and livestock. The instrument used is a Arcview 3.2 program and MINITAB release 14. Data processing is done by analysis of land cover change, analysis of changes in water quality, pollution load, pollution load carrying capacity, the analysis of public understanding, and study the influence of land cover changes on water quality. During the period 2005-2008 land cover changes in the Cisadane watershed area upstream shown by the decrease of forest area (72.88%), shrubs (88.18%), open land (91.14%), and the fields ( 97.52%), and increasing plantation area (102.46%), and residential (34.21%).Utilization of river water in the Cisadane watershed area upstream was quite high. For 93% of the 190 families interviewed using Cisadane River for MCK. Pollutant sources that can be seen is garbage (16%) and wastewater (30%). The dominant pollution load comes from domestic waste (4067.86 tons/month 4129.80 BOD and TSS) and livestock waste (3.24 tons/month of BOD and 17.05 tons/month TSS). This pollution load exceeds the capacity for BOD pollution load of each month and it ranged from 2484 tons/month to 3801 tons/month, while for TSS pollution load capacity not exceeding pollution load for each month. Changes in land cover and use of river water affects river water quality. This can be demonstrated by increasing in TDS (18 mg/l), BOD (20.8 mg/l), phosphate (0.303 mg/l), and COD (38 mg/l) which tends to exceed water quality standards. If viewed based on key parameters of water quality (BOD, COD, TSS), the correlation of test results on the α level 0.1 also could be concluded that there is a relationship between changes of land cover with water quality, although the significance level is relatively small. The icreasing of water quality parameters caused the decrease of Water Quality Index from 85,58 to 73,66, but the condition of the waters is still relatively moderate to good.
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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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