Judul: Study of Terigas Tangerine Degreening Originate from Sambas Regency of West Kalimantan
Abstrak: Terigas tangerine peel is still green even when it has reached acceptable internal maturity, meanwhile the green peel indicated immature fruit. Improving tangerine uniform yellow peel will also improve its aesthetic quality and price which could be taken by ethylene degreening technique. The objectives of this research were: (1) to study the ethylene concentration and trigger time of Terigas tangerine (Citrus nobilis var. chrysocarpa) degreening process, (2) to investigate influences of degreening on physicochemical and organoleptic changes of Terigas tangerine, (3) to determine the best ethylene consentration and trigger time of Terigas tangerine degreening process. Initial tangerine quality were analyzed before the tangerine were arranged inside box layered by LLDPE 0.06 mm plastic. After that the plastic was closed with the top of box remained open. Each box contained of 3 kg tangerines which finally exposed by 1000, 1500, and 2000 ppm of exogenous ethylene and without ethylene (control), with trigger time for 10, 20, and 30 hours. Soon after each trigger time was reached, the plastic was then opened and tangerines were placed at room temperature until their peel turned to be yellow. After that, quality of tangerines were analyzed which consisted of color changes, firmness, juice misture content, pH value, vitamin C content, total of chlorophyll and carotenoid, total soluble solid, and organoleptic. Results of the research showed that ethylene enhanced color of tangerine, increased total of carotenoid, and decreased total of chlorophyll. However it did not affect internal quality such as moisture content, firmness, total soluble solid, and vitamin C. Postharvest degreening also increased panelists preference of tangerine external color, nevertheless it did not affect sweetness, texture, and aroma of Terigas tangrine. The best treatment was 1000 ppm ethylene with trigger time for 30 hours. Uniform yellow peel of Terigas tangerine occured on the fourth day of storage at room temperature.
Keyword: tangerine, degreening, ethylene, trigger time, physicochemical

Judul: Perubahan Warna Kulit Buah Tiga Varietas Jeruk Keprok dengan Perlakuan Degreening dan Suhu Penyimpanan
Abstrak: Color is the main quality that determines the level of demand for citrus. Consumer prefers orange citrus, whereas green citrus have high productivity in Indonesia. It causes local citrus cannot compete with imported citrus. One way that can make local citrus compete with imported citrus is by degreening. This is research was conducted to study the effect of degreening and storage temperature on color changes of tangerine peel. Research was conducted from June until July 2013 at the Laboratory of Center for Tropical Horticulture Studies, IPB. This study was conducted on 3 varieties of tangerines (Chokun, Fremont, and Batu 55) separately. This research used a randomized complete factorial design group 2 factors with 3 replications. The first factor is degreening temperature (18°C and room temperature) and second factor is storage temperature (18°C and room temperature). The results showed that degreening treatment at 18°C and room temperature storage on all three varieties of tangerines have the highest CCI value at 15 HSP.
Keyword: value of Citrus Color Index., storage temperature, orange, degreening temperature

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.
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