Judul: Telaah fisik-ekonomis penggunaan dan pengusahaan lahan di wilayah daerah aliran sungai Way Rarem Kab. Lampung Utara
Abstrak: Sampai saat ini pengelolaan sumberdaya air masih terlalu dititikberatkan pada pemanfaatan air yang sudah tersedia, tanpa atau sedikit sekali memperhatikan proses alamiah dari ketersediaan air tersebut. Keadaan ini tampak dari berbagai usaha pembangunan infrastruktur seperti bendungan, waduk dan sarana irigasi, yang sering sekali kurang diimbangi dengan usaha untuk melestarikan kondisi optimum di bagian hulu Daerah Aliran Sungai (DAS) dimana aliran sungai bersumber. Berkaitan dengan usaha intensifikasi dan ekstensifikasi tanaman pangan, di Kabupaten Lampung Utara pada saat studi dilakukan sedang dibangun waduk dan sarana irigasi dengan memanfaatkan aliran sungai Way Rarem, yang diharapkan dapat mengairi areal sawah seluas 22 000 hektar di lokasi transmigrasi Way Abung. Sernentara pernbangunan waduk sedang berjalan, telah terjadi perubahan drastis dari pola penggunaan dan pengusahaan lahan dibagian hulu DAS way Rarem yang rnerupakan wilayah studi. Sebagian besar kawasan hutan telah berubah menjadi areal perkebunan rakyat, pemukiman, perladangan dan berbagai bentuk lahan terlantar. Keadaan semacam ini ditambah dengan terus meningkatnya jumlah penduduk pemukim diduga akan sangat mempengaruhi kelangsungan fungsi waduk dan sarana irigasi yang dibangun.
Keyword: River basin;

Judul: The development of sustainable water resources of way betung watershed, Bandar Lampung city
Abstrak: Way Betung watershed is one of the most potential watersheds as water supplier in Lampung Province and the most potential water resources for Bandar Lampung City particularly for potable water provided by regional water supplier company (PDAM). The ever increasing population and economic activities in Bandar Lampung City resulted in the increasing need of clean water. However, over time, the conditions of Way Betung watershed as water resources supplier have been declined. Therefore, to improve or to restore the conditions of Way Betung watershed, the forest and land rehabilitations programs are necessary. Thus research was aimed: (a) to study the impact of land use change in Way Betung watershed on its potential as water resources supplier of Bandar Lampung City, (b) to study the economic value of Way Betung water resources (c) to formulate sustainable water resources development plan of Way Betung watershed. The impact of land use change on the Way Betung water resources was analyzed by a regression method, and the annual economic value of water resources was analyzed by Willingness to Pay (WTP) method. The development plan of sustainable water resources of Way Betung watershed was arranged in five scenarios. To determine the best scenario, the simulations of the erosion level by the USLE method and the runoff volume by the SCS method were performed. The results showed that the land use change of Way Betung watershed (1991-2006) resulted in the increasing of the annual run off coefficient, the maximum daily discharge (Q max), and the decreasing of the daily minimum discharge (Q min), as well as the increasing of the river discharge fluctuation. The total annual economic value of water resources of Way Betung watershed was Rp101.1 billion/year and the total willingness to pay value for the rehabilitation of Way Betung watershed was Rp1.5 billion/year, which were derived from PDAM sector, tourism, water mineral companies, households and paddy field farmers in the upstream watershed. The best development of sustainable water resources of Way Betung watershed was the scenario-4 (the forest as much as 30% of watershed areas + alley cropping on mixed farms). Scenario-4 will reduce the erosion to lower than the tolerable soil loss (TSL), will decrease the fluctuation of monthly run off from 64.7 to 30.9, and the forest rehabilitation will be achieved in the best time (10 years with a scheme-B). Therefore, economically the water users community are willing to pay the rehabilitation costs (WTP) and socially it is accepted by the society.
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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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