Judul: Water quality of Jangkok River and its Relationship with Land Cover of the Jangkok Watershed, West Nusa Tenggara
Abstrak: Perubahan tutupan lahan berhutan menjadi peruntukan lain memunculkan sumber-sumber pencemaran air Sungai Jangkok. Tujuan penelitian ini adalah menganalisis kondisi kualitas air Sungai Jangkok, serta hubungan indeks kualitas air dengan penggunaan lahan di sekitar DAS Jangkok pada periode 2014-2019. Hasil analisis menggunakan Indeks Pencemaran (IP) sejak 2008-2019 mengalami fluktuasi, Kondisi kualitas air Sungai Jangkok dari hulu ke hilir dicirikan oleh beberapa parameter yang melebihi baku mutu air antara lain BOD, COD, amonium, nitrit, dan fosfor. Bagian hulu sungai memiliki status “memenuhi baku mutu” sementara di bagian tengah dan hilir berstatus “cemar ringan”. Analisis regresi menunjukkan bahwa tutupan lahan yang paling berpengaruh terhadap kualitas air Sungai Jangkok adalah lahan terbangun dan juga lahan kosong. Artinya apabila persentase luasan lahan kosong dan lahan terbangun meningkat, maka nilai IP juga akan meningkat. Nilai IP yang tinggi menunjukan pencemaran semakin buruk.
Keyword: Jangkok River, land cover, pollution index, river pollution

Judul: Kajian Perubahan Tutupan Lahan Sub DAS Citanduy Hulu terhadap Kualitas Air Sungai Citanduy Hulu
Abstrak: Along with the growth of population, the need of areas for residential is also increasing which interfere the existence of forest along the river upstream areas. Land use changes which occured on the watershed indicates the decrease of water quality for example in Citanduy Hulu subwatershed. The aim of this research is to assess the changing of land cover, water quality and the relation between both aspects. Analysis which was used in this research are changes of land cover, and Index of Water Quality-National Sanitation Foundation (IKA-NSF) calculation. Land cover type in Citanduy Hulu subwatershed which decreased are forest (33.27%), bushes (45.25%), and waterbody (47.59%). Land cover type which increased are residential (107.88%), paddyfield (98.52%), dryland farming (26.97%), and open space (74.02%). The water quality of Citanduy Hulu river is categorized as good. The value of IKA on Citanduy Hulu river showed the tendency to decline from 73.16 in 2003 to 70.42 in 2011. The decrease of forest, bushes, and waterbody also the increase of residential, paddyfield, dryland farming and open space at Citanduy Hulu subwatershed caused the decrease of water quality at Citanduy Hulu river.
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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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