Judul: Biodiversity of Insects in Pummelo ‘Bageng Taji’ (Citrus maxima (Burm.) Merr)
Abstrak: Serangga dapat berperan sebagai penyeimbang ekologi dan ekosistem perkebunan jeruk pamelo ‘Bageng Taji’ (Citrus maxima (Burm.) Merr). Jeruk pamelo juga memerlukan serangga untuk penyerbukan yang optimal. Penelitian ini bertujuan menganalisis keanekaragaman serangga di perkebunan jeruk pamelo ‘Bageng Taji’ di Bageng, Pati, Jawa Tengah. Pengamatan keanekaragaman serangga dilakukan dengan metode pengumpulan aktif berupa sweep net dan hand collecting serta metode pengumpulan pasif berupa pitfall trap. Serangga yang tertangkap pada perkebunan jeruk pamelo terdiri dari 8915 individu dalam 89 morfospesies, 41 famili dan 9 ordo yaitu Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Neuroptera, Odonata dan Orthoptera. Diversitas serangga pada penelitian ini termasuk dalam kategori sedang dengan kemerataan rendah (H’ = 2,22) (E = 0,49) dan tidak ada spesies yang mendominasi (D = 0,26). Serangga terbanyak yang dikoleksi dengan metode pengumpulan aktif yaitu Hypolimnas bolina (Nymphalidae, Lepidoptera) sedangkan dengan pengumpulan pasif yaitu Nylanderia sp. (Formicidae, Hymenoptera). Serangga yang ditemukan umumnya berperan sebagai herbivor., Insects have a role in balancing of ecology and ecosystem in the pummelo ‘Bageng Taji’ (Citrus maxima (Burm.) Merr) plantations. Pummelo also required insects for optimal pollination. This study aimed to analyze the diversity of insects in pummelo ‘Bageng Taji’ plantations in Bageng, Pati, Central Java. Observation of insects diversity was carried out using active sampling methods, i.e., sweep nets and hand collecting and passive sampling methods, i.e., pitfall traps. This research recorded 8915 individuals in 89 morphospecies, 41 families and 9 orders namely Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Neuroptera, Odonata and Orthoptera. Analysis of insects diversity showed in moderate category (H’ = 2,22) with low evenness (E = 0,49) and no species dominated (D = 0,26). Highest number of individual insects collected by active sampling was Hypolimnas bolina (Nymphalidae, Lepidoptera) while used passive sampling was Nylanderia sp. (Formicidae, Hymenoptera). Insects found generally categorized as herbivores.
Keyword: ecology, morphology, Pati Regency, Pitfall trap, Sweep net

Judul: Biodiversitas  Serangga pada Perkebunan Jeruk Pamelo (Citrus maxima (Burm.) Merr.) di Desa  Bageng, Kecamatan Gembong, Kabupaten Pati
Abstrak: Serangga memiliki keanekaragaman yang sangat tinggi dan kemampuan adaptasi yang baik pada berbagai habitat. Kajian mengenai serangga pada perkebunan jeruk pamelo di Indonesia belum banyak dilaporkan. Penelitian ini bertujuan menganalisis keanekaragaman serangga dengan tiga metode koleksi berupa insect net, yellow pan trap, dan Malaise trap pada perkebunan jeruk pamelo di Pati, Jawa Tengah. Pengamatan keanekaragaman serangga dilakukan dengan metode scan sampling dengan mencatat nama spesies dan jumlah individu serangga. Koleksi serangga juga dilakukan dengan menggunakan yellow pan trap dan Malaise trap. Serangga yang dikumpulkan berjumlah 4506 individu yang terdiri atas 128 spesies (morfospesies) dalam 52 famili. Serangga yang ditemukan terbanyak termasuk dalam ordo Hymenoptera, famili Formicidae. Jumlah individu dan spesies serangga paling banyak didapatkan dengan Malaise trap (2349 individu, 77 morfospesies). Diversitas serangga di perkebunan jeruk pamelo termasuk tinggi (Hʹ=3,16, E=0,18) dengan indeks dominansi sebesar 0,15. Salah satu spesies serangga yang banyak ditemukan adalah Anoplolepis gracilipes. Jumlah individu serangga memiliki korelasi positif terhadap suhu, kelembapan udara, dan intensitas cahaya., Insects have a very high diversity and good adaptability in various habitats. Studies on insects in pummelo plantations in Indonesia have not been widely reported. This study aims to analyze the diversity of insects using three collection methods, insect net, yellow pan trap, and Malaise trap in pummelo citrus plantations in Pati, Central Java. Observation of the diversity of insects was carried out using the scan sampling method by recording the name of species and the number of individual insects. Insect collection was also carried out using yellow pan trap and Malaise trap. The collected insects totally 4506 individuals consisting of 128 species (morphospecies) belonging to 52 families. Most insects are included in the Hymenoptera order, family Formicidae. The highest number of individuals and insect species was collected by Malaise traps (2349 individuals, 77 morphospecies). Insect diversity in pummelo plantations was high (Hʹ=3.16, E=0.18) with a dominance index of 0.15. One species of insect that is commonly found is Anoplolepis gracilipes. The number of individual insects has a positive correlation with temperature, humidity, and light intensity
Keyword: insect net, Malaise trap, scan sampling, yellow pan trap

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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