Judul: Evaluation of several Preservatives for Storage of Mexicana Grass Cuttings (Euchlaena mexicana Schrad)
Abstrak: Rumput Meksiko (Euchlaena mexicana Schrad) tidak dapat dibudidayakan dengan biji. Oleh sebab itu perlu dilakukan pengawetan pada stek, agar dapat di distribusikan ke tempat yang lebih jauh. Permasalahan yang sering terjadi pada pengiriman stek adalah terjadinya kerusakan secara fisik maupun rusak karena faktor lain seperti mikroba dan fungi, oleh karena itu perlu ada metode pengawetan stek. Penelitian ini bertujuan untuk mengetahui bahan dan alat yang tepat digunakan sebagai pengawet dan menentukan lama masa simpan yang terbaik untuk stek rumput Meksiko (Euchlaena mexicana Schrad). Rancangan percobaan yang digunakan adalah Rancangan Acak Lengkap (RAL) pola faktorial dengan pengulangan 5 kali. Faktor A adalah perlakuan berupa 4 jenis bahan atau alat pengawet: cairan gula 2%, cairan lilin, silica gel dan mesin pendingin (refrigerator) dan faktor B berupa 5 jenis lama penyimpanan: 3, 6, 9, 12 dan 15 hari. Bahan yang digunakan adalah stek rumput Meksiko (Euchlaena mexicana Schrad) sebanyak 625 potong stek. Peubah yang diukur adalah: keadaan umum stek, awal pertumbuhan setelah tanam, daya tumbuh, penyusutan bobot stek dan tinggi vertikal. Hasil penelitian menunjukkan bahwa pada perhitungan penyusutan bobot stek terlihat adanya interaksi antara perlakuan bahan pengawet dengan lama penyimpanan (P<0,05), dimana semakin lama penyimpanan maka penyusutan bobot semakin besar. Terdapat interaksi yang nyata antara daya tumbuh dan tinggi vertikal dengan lama penyimpanan (P<0,05), semakin lama penyimpanan maka daya tumbuh dan tinggi vertikal semakin menurun. Kesimpulan dari penelitian ini adalah stek rumput Meksiko (Euchlaena mexicana Schrad) dapat disimpan dengan kualitas yang baik selama 15 hari dengan menggunakan pengawet/alat refrigerator.
Keyword: 

Judul: Uji pengawetan terhadap daya simpan bahan tanam stek rumput gajah (Pennisetum purpureum Schummach)
Abstrak: Raising elephant grass (Pennisetum purpureum Schummach) generally use the cuttings vegetative planting material. Breeding by generative (seeds) can not be done because of infertility. Breeders or elephant grass cuttings manufactures still can not distribute more than a week, because it is easily damaged by external factors such as microbes and fungi. Therefor it is necessary that both storages methods cuttings that have a longer shelf life. The aim of this study was to determine the materials and tools that can extend the life of old cuttings and determine the shelf life is best for planting material cuttings of elephant grass. Experimental design used was completely randomized design (CRD) factorial with repeated 5 times. A factor is a preservation treatment is 4 types of materials or equipment that is preservative 2% liquid sugar, liquid wax, silica gel, an refrigerator (4 oC) and factor B are 5 levels of storage time of 3, 6, 9, 12, and 15 days. The materials used are cutting grass counted 625 pieces of cuttings. The variables measured were the general state of cuttings, weight decrease, early growth after planting, growing power, and vertical height. Results showed that the real interaction (P<0,05) the weight decrease significant cuttings between the used of preservatives with storage time, the interaction occurs in sugar preservatives, silica gel and control. the interaction showed a point of intersection between the sugar, silica gel and control over storage time chart at approximately 13 days. Intersection indicates that the maximum point of planting cuttings storage materials are given preservative sugar, silica gel, and control is about 13 days. Storage time significantly (P<0,05) the ability of grow, where teh storage time of 15 day showed a significant reduction in the growth of storage longer than others. Preservative retention and significantly (P<0,05) to the vertical height, where the storage time of 15 day showed higher average vertical drop significantly and the average height of the highest vertical is when using wax and sugar preservatives. The conclusion of this study is the shelf life cuttings of elephant grass (Pennisetum purpureum Schummach) can be improved by using sugar preservatives, silica gel, wax, and refrigerator at 4 oC for 15 days storage time and quality is good for 15 days of shelf life that is using a refrigerator at 4 oC.
Keyword: 

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
Keyword: