Judul: Optimization of Pressing Temperature and Time of Composite Molding of Sweet Sorghum Bagasse with  Sucrose-Based Adhesive
Abstrak: Moulding komposit yang ramah lingkungan diperlukan pada produk yang digunakan dalam kehidupan manusia sehari-hari seperti kitchen set, komponen kendaraan, bagian bangunan, dll. Oleh karena itu, bagas sorgum sebagai limbah perkebunan sorgum dan perekat asam sitrat-sukrosa merupakan salah satu sumber daya berkelanjutan yang dapat digunakan sebagai bahan baku pembuatan moulding. Akan tetapi, kondisi kempa yang optimum dalam pembuatan moulding bagas sorgum yang direkat dengan asam sitrat-sukrosa belum diketahui. Oleh karena itu, suhu dan waktu kempa optimum diselidiki. Variasi suhu dan waktu pengempaan masing-masing adalah 180, 200, 220 ºC dan 8, 10, dan 12 menit. Hasil penelitian menunjukkan bahwa kekuatan lentur dan stabilitas dimensi moulding meningkat dengan meningkatnya suhu pengempaan. Moulding dengan kondisi pengempaan panas 200 ºC dan 12 menit memiliki nilai MOE (2,86 Gpa) dan MOR (16,70 Mpa) lebih tinggi daripada kondisi pengempaan lainnya. Dengan demikian, 200 ºC dan 12 menit masing-masing adalah suhu dan waktu kempa yang optimum., Eco-friendly moulding composite is necessary in all products which is used in daily life of human being such as kitchen set, body part of vehicle, building part, etc. Therefore, sorghum bagasse as a waste of sorghum plantation and sucrose-citric acid as one of the sustainable resources were used as raw material of the moulding. However, the optimum of pressing condition in the manufacturing of sorghum bagasse moulding bonded with sucrose-citric acid does not determine. Therefore, the optimum of pressing temperature and time were investigated. The variation of pressing temperatures and time were 180 ºC, 200 ºC, 220 ºC and 8, 10, and 12 minutes, respectively. The results showed that the bending strength and dimensional stability of the moulding increased with increasing the pressing temperature. The moulding with 200 ºC and 12 minutes of hot pressing condition has the MOE (2.86 Gpa) and MOR (16.70 Mpa) higher than those of the other pressing condition of the moulding. Thus, 200 ºC and 12 minutes were pressing temperature and time optimum, respectively.
Keyword: Asam sitrat, Moulding, Suhu kempa, Sukrosa, Waktu kempa, Citric acid, Molding, Pressing temperature, Pressing time, Sucrose

Judul: Sorghum Bagasse Particleboard Bonded by Bio-Adhesive with Nano-Catalyst Addition
Abstrak: Pengembangan papan partikel bagas sorgum menggunakan perekat hayati dengan penambahan nanokatalis berpotensi menghasilkan papan partikel ramah lingkungan dengan sifat fisis-mekanis yang lebih baik. Penelitian ini bertujuan untuk mengembangkan papan partikel berbahan baku biomassa bagas sorgum dan perekat hayati molase-asam sitrat dengan penambahan nanokatalis seng oksida (ZnO) dan grafena oksida (GO). Papan partikel dibuat dengan kerapatan target 0,8 g/cm3, berukuran 35 x 35 x 0,6 cm3 dan dikempa panas pada suhu 200 ○C selama 10 menit dengan tekanan 10 MPa. Sifat fisis dan sifat mekanis papan partikel dievaluasi menggunakan standar JIS A 5908-2003. Papan partikel berperekat molase-asam sitrat dengan penambahan nanopartikel ZnO merupakan perlakuan terbaik pada penelitian ini. Papan partikel molase-asam sitrat ZnO memiliki kerapatan sebesar 0,79 g/cm3, kadar air sebesar 6,22%, pengembangan tebal sebesar 6,49%, modulus of rupture sebesar 127,16 kgf/cm2 dan keteguhan rekat sebesar 2,26 kgf/cm2. Sifat fisis dan mekanis papan partikel molase-asam sitrat ZnO telah memenuhi standar JIS A 5908-2003. Berdasarkan hasil analisis FTIR diketahui bahwa pada papan partikel bagas sorgum berperekat hayati dengan penambahan nanopartikel telah terbentuk ikatan ester., The development of sorghum bagasse particleboard using bio-adhesive with the addition of nanocatalysts has the potential to produce environmentally friendly particleboard with better physical-mechanical properties. This study aims to develop particleboard made from sorghum bagasse biomass and molasses-citric acid bio-adhesive with the addition of zinc oxide (ZnO) and graphene oxide (GO) nanocatalysts. The particleboard was made with a target density of 0.8 g/cm3, 35 x 35 x 0,6 cm3 in dimensions and hot pressed at 200 °C for 10 minutes under 10 MPa pressure. The physical and mechanical properties of the particleboard were evaluated using the JIS A 5908-2003 standard. Particleboard bonded with molasses-citric acid with ZnO nanoparticles addition was the best treatment in this study. The molasses-citric acid ZnO particleboard has density value of 0.79 g/cm3, moisture content value of 6.22%, thickness swelling value of 6.49%, modulus of rupture value of 127.16 kgf/cm2 and a internal bonding value of 2.26 kgf/cm2. The physical and mechanical properties of molasses-citric acid ZnO particleboard have satisfied the JIS A 5908-2003 standard. Based on the results of FTIR analysis, it is known that the bio-adhesive sorghum bagasse particleboard with the addition of nanoparticles has formed ester bonds.
Keyword: citric acid, molasses, graphene oxide, sorghum bagasse, zinc oxide

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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