Judul: Perbaikan Mutu Biodiesel Hasil Proses Fraksinasi dengan Kandungan Metil Oleat (C18:1) Dominan untuk Penerapannya sebagai Bahan Bakar
Abstrak: Fractionation of palm olein biodiesel using fractional distillation system is used to separate dominant methyl palmitic (C16) with dominant methyl oleic (C18:1). This biodiesel fraction contains dominant of methyl oleic (C18:1), has a good characteristic in lower cloud point that possibly be applicated as a fuel in four season country. Bentonite are used in this research with the view of its usefulness in lowering viscosity and acid number. The purpose of this study is to obtain the best characteristics of biodiesel as a fuel appropriate to the biodiesel standard, and to obtain the best bentonite concentration used to improve the unappropriate parameter. This study was conducted using completely randomized design. Biodiesel quality improvement is done by using experimental factor of bentonite concentration (1%, 3%, and 5%). The use of bentonite experimentally could lowering acid number and kinematic viscosity. Compared to the blank (control), biodiesel with 1% of bentonite concentration could give the best result in lowering kinematic viscosity.
Keyword: 

Judul: Fraksinasi Metil Ester Olein Menggunakan Fractional Distillation System untuk Menghasilkan Metil Ester Palmitat (C16 )
Abstrak: Palm olein biodiesel is consist of fatty acid methyl ester mixture. Separation of methyl ester fraction can be performed by fractionation technique. Fractional distillation system is used in this research to separate the dominant of methyl ester palmitic (C16). Fractional distillation system composed of several main components i.e boiling vessel, column with packing, condenser, vacuum unit, water cooling unit, heating unit and reciever vessel. This study was conducted using completely randomized factorial design. Fractionation process is done by using two experimental factors i.e temperature process (225 oC, 230 oC, 235oC) and processing time (10 and 12 hours). Separation process produces two fraction of biodiesel, distillate and residual biodiesel. The best condition to separate dominant of methyl ester palmitic faction obtained at the experimental unit temperature 235oC and processing time of 12 hours. The purity of C16 methyl ester fraction is 80,17% (w/v). Residual biodiesel can be obtained as dominant of methyl ester oleic (C18:1) is 60,80% (w/v) in experimental unit 235oC and 10 hours.Distillate biodiesel has several changes in physicochemical properties such as decreasing of density value, decreasing of iodine value, decreasing of saponification value, decreasing of acid number and levels of FFA compared to the initial biodiesel. Physicochemical changes in distillate caused by the composition of FAME biodiesel that is dominated by saturated methyl esters and lower molecular weight. Meanwhile, residual biodiesel is physicochemically changes by increasing density value, increasing of iodine value, increasing of saponification value, increasing of acid value and levels of FFA. This changing is caused by unsaturated methyl ester, higher molecular weight and also higher content of free fatty acids which are formed due to high temprature during the process
Keyword: 

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf