Judul: Model Penjadwalan Keberangkatan Bus dengan Strategi Alternating Deadheading: Studi Kasus PO Raya
Abstrak: Bus Departure scheduling is one of important aspects in managing a bus company in order to minimize the operational cost. This scheduling is formulated as a linear integer programming model. The purpose of this model is to arrange buses from each city to meet transportation demand. The strategy of the model is to develop bus scheduling using deadheading. The deadheading strategy will be used if there is an unbalancy in the number of buses operated in one or more cities. The model with deadheading is one of efforts to minimize the frequency of bus departure in order to increase efficiency of the bus operation.
Keyword: alternating deadheading, linear integer programming, bus scheduling

Judul: Penentuan Rute Bus Karyawan menggunakan Pemrograman Linear Integer
Abstrak: Tulisan ini memberikan formulasi masalah penentuan rute bus karyawan menggunakan pemrograman linear integer. Rute setiap bus berawal dan berakhir di suatu tempat (depot) untuk menjemput karyawan melalui beberapa pos. Setiap pos dikunjungi tepat sekali oleh suatu bus dengan memperhatikan kapasitas setiap bus dan jarak tempuh maksimum setiap bus sehingga dapat dipastikan bahwa bus sampai depot (tempat kerja) sebelum jam kerja dimulai. Fungsi objektif masalah ini adalah meminimumkan biaya operasional seluruh bus yang dioperasikan. Biaya operasional setiap bus diasumsikan sepadan dengan biaya perawatan tetap dan biaya penggunaan yang sesuai dengan jarak perjalanan bus tersebut. Pada contoh studi kasus dengan menggunakan data hipotetik dalam karya ilmiah ini, biaya yang paling minimum diperoleh jika digunakan 4 unit bus. Total jarak yang ditempuh oleh keempat unit bus dalam menjemput atau mengantar karyawan adalah 247 km. Total biaya yang harus dikeluarkan untuk biaya operasional bus karyawan per harinya adalah 894000 rupiah.
Keyword: Integer linear programming, Branch-and-bound

Judul: Extraction and Characteristic of Collagen and Nanoparticle Collagen from the Skin of Stingray Fish (Pastinachus solocirostris) as Ingredient of Cosmetics.
Abstrak: Isolation of collagen from the skin of stingray fish (Pastinachus solocirostris) has been successfully conducted with three stages: first soaked in 0.05 M NaOH with a sample/solution ratio of 1:10 (w/v) for 6 hour, second soaked in 0.1 M acetic acid with a sample/solution ratio of 1:6 (w/v) for 2 hour, and third extraction with destilated water at temperature 40 C for 2 hour with a yield of 14.475 % (wet base). Nanoparticle collagen was made with desolvation method using etanol as a desolvating agent with a collagen solution/etanol ratio of 1:1. Yield of nanoparticle collagen was 9.64% (wet base) with particle size of 185.24 nm. Collagen and nanoparticle collagen is in the form of white powder with whiteness degree 72.48% and 60.03%, respectively. Protein is the major component in collagen and nanoparticle collagen (86.97% and 86.18%) with trace amount of ash (0.17% and 0.13%) and fat (0.19% and 0.25%), respectively. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns, amino acid composition, and fourier transform infrared (FTIR) spectra of both collagen and nanoparticle collagen were characterized as type I collagens. Nanostructural analysis of collagen and nanoparticle collagen by Scanning Electron Microscopy (SEM) shows that both were separate aggregates. Other characteristics of collagen and nanoparticle collagen were: Tmax of 165.88 C and 156.63 C; Viscosity 292.33 cP dan 110 cP; pH 5.00 dan 4.93; respectively. Collagen has highest solubility at pH 7 and the isoelectric point at pH 6, 9, and 10. Therefore, nanoparticle collagen has highest solubility at pH 3 dan and the isoelectric point at pH 6. Collagen and nanoparticle collagen from skin of stingray fish (Pastinachus solocirostris) has a characteristic for a potential use as a cosmetic ingredient.
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