Judul: Dynamics system modeling for rice stock
Abstrak: Produksi beras di Indonesia dicirikan oleh banyaknya pihak yang terlibat dan luasnya wilayah distribusi. Terdapat dua sumber utama pengadaan beras di Indonesia, yaitu produksi dalam negeri dan beras impor. Dua jenis beras tersebut didistribusikan ke seluruh negeri melalui berbagai pemasaran dan alat distribusi. Dinamika pasokan beras dan distribusinya terutama dipengaruhi oleh musim, luas panen, produktifitas lahan, harga di dalam negeri, harga beras di luar negeri, bea masuk, tindakan pemerintah melalui Perum BULOG, dan kualitas infrastruktur. Penelitian ini bertujuan untuk menghasilkan sebuah model sistem dinamis yang dapat digunakan untuk mempelajari perilaku sediaan beras di Indonesia sepanjang tahun. Metode yang digunakan adalah metoda simulasi dengan memanfaatkan perangkat lunak ithinkTM. Sistem distribusi beras diuraikan menjadi sepuluh subsistem yang meliputi sub sistem petani, pedagang pengumpul, penggilingan padi, Koperasi Unit Desa (KUD), grosir/swasta, importir, Bulog, stok nasional, pengecer dan subsistem konsumen atau pengguna akhir. Interaksi antar subsistem divisualkan dengan diagram kausal (causal diagram) yang disusun mengikuti pendekatan sistem. Sensitifitas model dapat diperiksa dengan menjalankan model menggunakan satu set nilai awal parameter dan peubah utama, serta memvariasikan nilai salah satu peubah.
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Judul: Dynamics System Modeling for Rice Stock
Abstrak: Rice production in Indonesia is characterized by large number of people and institutions involved in the business and wide spread of distribution area. There are two kinds of rice sources namely in country farmers production and the imported one. From these two sources rice is distributed throughout the country through many channels of marketing and distribution. The dynamics of rice supply and its distribution is mainly affected by factors of season, harvest field availability and its productivity, rate of harvesting failure, in country prices, import barrier, government involvement, and quality of infrastructure. A system dynamics model of rice stock was constructed using ithinkTM software. The model attempts to figure out the behaviour of rice stock system by simulation technique. The system was represented by ten subsystems which are interacting one to another. These ten subsystems were farmers, rice millings, KUD, collector traders, Bulog, grociers, importers, national stock. The interaction between each subsystem is depicted by a causal diagram, following the systems dynamics approach. The sensitivity of the model can be tested by running the model under certain set of values of key parameters and variables. The simulation resulted in two important findings. First, the model was able to picture the dynamics of rice distribution among ten subsystems assigned. Second, the value of stocks at each subsystem were considerably resembling the actual stocks at each subsystem. These results enabled the model to be used as a predicting tool or simulation tool for rice stock distribution.
Keyword: Rice stock, dynamic system

Judul: Hydroxyapatite-Chitosan Composite Coating on Stainless Steel 316 to Improve Corrosion Resistance
Abstrak: Metals that were used in bone implantation should have good corrosion resistance that were not easily corroded when implanted into the body. Metal corrosion resistance of stainless steel 316 can be enhanced through the metal coating by hydroxyapatite-chitosan composite with composition ratio of hydroxyapatite (gram) and chitosan 3% (mL) 0.2:0, 0.2:0.1, 0.2:0.5, 0.2:1.0, and 0.2:1.5. Besides improving the corrosion resistance of metal, the presence of chitosan also maintain the position of hydroxyapatite on metal surfaces. Corrosion resistance increases with increasing amount of chitosan added and the best composition of hydroxyapatite-chitosan composite was 0.2:1.0.
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