Judul: Kepadatan dan Persebaran Parmarion martensi pada 15 Jenis Sayuran di Agropolitan Desa Gombong, Kecamatan Belik, Kabupaten Pemalang
Abstrak: Parmarion martensi merupakan siput setengah telanjang (semi-slug) yang memiliki cangkang kecil tereduksi. Siput ini menjadi hama dan menyerang tanaman. Tujuan penelitian ini adalah mengamati dan mempelajari kepadatan dan persebaran ukuran serta aktivitas makan P. martensi pada 15 jenis tanaman sayuran di Agropolitan Desa Gombong, Kecamatan Belik, Kabupaten Pemalang. Penentuan lokasi persebaran sampel dilakukan secara acak dengan membuat plot 1m x 1m setiap satu jenis sayuran dengan 3 kali ulangan. Pengamatan aktivitas makan P. martensi pada setiap jenis sayuran diamati secara visual. Pengukuran panjang tubuh P. martensi dilakukan setiap kali pengamatan. Pola kepadatan dan persebaran diketahui melalui analisis data menggunakan metode kuadrat dan Indeks Persebaran Morisita. Hasil penelitian menunjukan bahwa kepadatan P. martensi tertinggi ditemukan pada kacang buncis (Phaseolus vulgaris) sebesar 23,3 ind/m2, sedangkan kepadatan terendah ditemukan pada wortel (Daucus carota) dan seledri (Apium graviolens) sebesar 1,0 ind/m2. Pola persebaran P. martensi mengelompok dan lebih didominasi ukuran besar. P.martensi lebih suka memakan bagian daun.
Keyword: Densitas, hama, semi-slug

Judul: Kepadatan dan Persebaran Deroceras laeve dan Meghimatium bilineatum pada 10 Jenis Sayuran di Agropolitan, Cipanas
Abstrak: Deroceras laeve and Meghimatium bilineatum are slugs which are pest, that attacks the vegetables crop. The aims of this research is to study the density and distribution (pattern, feeding activity, and size) of D. laeve and M. bilineatum on 10 types of vegetables at Agropolitan, Cipanas. Sampling was conducted by quadrat method randomly. The highest density of D. laeve was 13.33 ind/m2 on Allium fistulotum and the lowest was 4 ind/m2 on Cripsum frutescens. The highest density of M. bilineatum was 6.22 ind/m2 on Solanum lycopersicum whereas the lowest was 0.56 ind/m2 on Daucus carota. Distribution Pattern of D.laeve and M. bilineatum is group. Distribution of D. laeve of small size (< 1.5 cm), medium (1.5−2.5 cm), and large (> 2.5 cm) were found in 9 different types of vegetables. Distribution of M. bilineatum of small size (< 2 cm) are rare, while the medium size (2−4 cm) and large (> 4 cm) were found in the 4 types of vegetables. Both D. laeve and M. bilineatum were prefer to eat leave than stems and tuberous root.
Keyword: Deroceras laeve, Meghimatium bilineatum, density, distribution

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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