Judul: Inventory model of single stocking point-single commodity with a constant demand rate
Abstrak: Inventori merupakan salah satu aset penting bagi suatu perusahaan dan pengolahan inventori yang baik dapat meningkatkan pendapatan dari penjualan produk bagi perusahaan tersebut. Tujuannya adalah untuk menyediakan produk dengan mutu yang baik dalam jumlah dan waktu yang sesuai guna memenuhi permintaan. Karya ilmiah ini bertujuan menentukan penyelesaian model inventori single stocking point-single commodity dengan tingkat permintaan konstan. Jumlah barang yang harus dipesan pada setiap pemesanan didapatkan dengan menurunkan persamaan dari rataan total biaya pemesanan tahunan. Beberapa asumsi diterapkan pada model inventori ini sehingga didapatkan suatu model dasar Economic Order Quantity. Kesimpulan yang didapatkan adalah model inventori dengan kekurangan persediaan memiliki nilai rataan biaya tahunan lebih besar dibandingkan dengan model inventori manakala kekurangan persediaan tidak diperbolehkan., Inventory is one of important assets for a company and a good inventory management could increase income. The goal of this work is to provide good quality products available at appropriate amount and time. This paper aims to determine the solution of inventory model of single stocking point-single commodity with constant demand rate. The amount of products to be ordered in every order can be obtained via derivation of the average of annual total order cost. Some assumptions are applied to this inventory model to obtain a basic Economic Order Quantity model. The conclusion of this paper is that the inventory model with shortage has bigger average of annual order cost than that without shortage. Keywords: economic order quantity, inventory model
Keyword: economic order quantity, model inventori

Judul: Optimization of Inventory Model with Constant Level of Deterioration and Credit Payment
Abstrak: Persediaan adalah stok barang yang disimpan oleh distributor atau perusahaan yang dijual kepada pelanggan di waktu yang akan datang. Untuk memenuhi permintaan pelanggan, diperlukan pengendalian persediaan dengan menentukan kapan barang akan dipesan dan kuantitas barang yang dipesan agar biaya total yang dikeluarkan minimum. Dalam sistem ini terjadi beberapa jenis barang yang dapat mengalami kerusakan sehingga tidak dapat disimpan dalam jangka waktu yang lama. Selain itu, distributor memiliki situasi tidak dapat membayar biaya pembelian secara tunai kepada pemasok atau manufacturer sehingga dilakukan pembayaran dengan sistem kredit. Karya ilmiah ini membahas model Economic Order Quantity dengan tingkat kerusakan konstan dan pembayaran secara kredit. Untuk itu diformulasikan masalah persediaan untuk menentukan banyak pesanan dan periode pengisian ulang sehingga dapat meminimumkan biaya total persediaan. Selain itu, ditinjau pula pengaruh tingkat kerusakan, tingkat suku bunga, dan batas waktu kredit terhadap periode pengisian ulang, kuantitas barang yang dipesan, dan biaya total persediaan., Inventory is stock items stored by distributors or companies that are sold to customers in the future. In order to meet customer demand, inventory control is needed by determining the order time and the order quantity so that the total costs incurred are minimum. In this system, several types of items can deteriorate so that they cannot be stored for a long period of time. Furthermore, the distributor has a situation where he cannot pay the purchase cost in cash to the supplier or manufacturer so that payment is made using the credit system. In this work, we discuss the Economic Order Quantity model with constant level of deterioration and credit payments. For this purpose, an inventory problem is formulated to determine the number of orders and the replenishment period so as to minimize the total cost of inventory. In addition, it is also examined the effect of the level of deterioration, interest rates, and credit times limits on the replenishment period, the quantity of items ordered, and the total cost of inventory.
Keyword: credit, Economic Order Quantity, inventory, optimization

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