Judul: Keanekaragaman dan kelimpahan artropoda pada pertanaman bawang daun dan wortel yang ditanam secara monokultur dan tumpangsari
Abstrak: Green onion is a seasonal crop with ecological conditions that are frequently changed. This makes unstable condition between populations of pests and natural enemies (predators, parasitoids and pathogens). Brief observations in the field found that pest infestations on carrot fields were frequently low. Results of several studies indicated that carrot could attract parasitoids of insect pests. The objective of this research was to study the diversity and abundance of arthropods on green onion and carrot grown in monoculture and intercropping. Experiment with four treatments and four replications was set in randomized complete block design. The treatments were: P1) green onion grown in monoculture; P2) green onion sprayed with carrot leaf extract; P3) green onion and carrot grown in intercropping; and P4) carrot grown in monoculture. Observations of arthropods were conducted by setting pitfall traps and yellow sticky traps weekly. Collected arthropods were identified by using Introduction to The Study of Insects, Insects of Australia, and Hymenoptera of The World. Data were analyzed with Shanon- Wienner index, and analysis of variance by using Minitab 17. The result indicated that the culture system of green onion and carrot did not affect diversity of arthropods for the whole season. The arthropod community on green onion and carrot was dominated by Liriomyza spp. (Diptera: Agromyzidae), ants (Hymenoptera : Formicidae), and Collembola.
Keyword: Bogor Agricultural University (IPB), intercropping., green onion, diversity, carrot, Arthropods

Judul: Pengaruh cara budidaya bawang daun terhadap serangan pengorok daun Liriomyza spp. dan parasitoidnya
Abstrak: Biological control by natural enemies such as parasitoids is considered as an effective pest control. Intercropping can be done to manipulate the habitat to make suitable for parasitoids. The aim of this research was to study the effect of intercropping of green onion with carrots and spraying of carrot leaf extract on the infestation of leaf miner, Liriomyza spp. (Diptera: Agromyzidae) on green onion and parasitization rate of parasitoids on the pest. The experiment consisted of three treatments and four replications arranged in randomized complete block design (RCBD). The treatments were 1) green onion grown in monoculture system, 2) green onion grown in monoculture system and sprayed with carrot leaf extract, and 3) green onion grown in intercropping system with carrot. Infestation of leaf miner, leaf miner population and parasitization were observed weekly by direct observation and using sticky trap. Two spesies of leafminer, i.e. Liriomyza huidobrensis and L. chinensis were found infesting green onion. Intercropping carrot with green onion and application of carrot leaf extract not affect the infestation of leafminer on green onion
Keyword: Bogor Agricultural University (IPB), parasitoids, Liriomyza spp., intercropping, green onion, carrots

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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