Judul: Masalah kontrol optimum pada sistem inventori produksi
Abstrak: Pengendalian persediaan merupakan salah satu fungsi manajerial perusahaan yang sangat penting, karena melibatkan investasi dana. Bila perusahaan menanamkan terlalu banyak dananya dalam persediaan maka akan menyebabkan biaya penyimpanan yang berlebihan. Selain itu, barang yang terlalu lama disimpan berisiko mengalami kerusakan. Sebaliknya, bila perusahaan tidak mempunyai persediaan yang mencukupi, dapat mengakibatkan kehilangan penjualan dan kehilangan pelanggan.
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Judul: Kontrol Optimum Sistem Inventori-Produksi dengan Laju Kerusakan Barang Menyebar Weibull
Abstrak: Inventory control is a natural action that everyone undertakes, as we keep foods, clothes, pens, papers, and many other goods. For companies, inventory control is an important thing to do because it manages the capital assets and organizes the availability of items for customers. Production-inventory system is a dynamic model (a function of time) so that it can be presented as a problem of optimal control. This paper is concerned with an optimal control of a production-inventory system with deteriorating items. It is assumed that the deterioration rate follows a two parameters Weibull distribution. In this work we investigate continuous and discrete models. Optimal condition for continuous model is derived by using Pontryagin maximum principle, where the solution is a second order differential equation which solved numerically by using finite difference method. While discrete production-inventory system is solved by Lagrange technique, with the optimal solution is obtained by solving difference equations recursively.
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Judul: Studi Taksonomi Katak Subgenus Papurana (Lesson, 1831) dari Halmahera (Anura, Ranidae, Hylarana), Studi Taksonomi Katak Subgenus Papurana (Lesson, 1831) dari Halmahera (Anura, Ranidae, Hylarana
Abstrak: I reevaluated taxonomic of subgenus Papurana position from Halmahera based on morphological and molecular analyses. My results show that two separate species occur on the Halmahera Island, each nested within two distinct clades (hereafter papua clade and celebensis clade), one of which corresponds to H. moluccana (celebensis clade) and the other to an unidentified species (papua clade). By p-distance ranging from 6.9 to 11.5% on the 16S rRNA gene, the unidentified species (Hylarana sp.) is genetically different from all congeners of the papua clade. The Hylarana sp. can be distinguished from all congeners by following combination of charactes: vomer teeth in two oblique rows with narrow inter-vomer distance; snout rounded dorsally; dorsum with few scattered cone-shaped tubercles that are black with white tips; distinct skin folds (ridges) on the dorsal side of the thigh coinciding with dark brown cross bars; a marbled pattern on the ventral side of the thigh and yellowish groin. I also present new data for H. daemeli, H. volkerjane, and H. arfaki from the western region of Papua. Furthermore, I found that H. celebensis has numerous mtDNA lineages, indicating cryptic diversity within the celebensis clade. The discovery of two separate species on Halmahera necessitates more research into the biogeographic history of Hylarana in Northern Moluccas.
Keyword: frog, Halmahera, Hylarana, morphology, Papurana, phylogenetic