Judul: Influence of Incandescent Bulb’s Lighting  Period on Lumbricus rubellus’s Productivity
Abstrak: Cacing tanah merupakan salah satu satwa harapan yang memiliki potensi besar sebagai ternak pendukung dari peternakan terintegrasi. Lumbricus rubellus merupakan cacing berukuran relatif kecil dengan panjang antara 4-6 cm dan bewarna merah kecokelatan atau merah-violet. Cacing tanah berkembang dengan mengonsumsi bahan organik yang berada di lingkungan sekitarnya. Keberagaman mikroorganisme di suatu ruang ditentukan oleh beberapa faktor seperti temperatur, kelembaban, dan paparan cahaya. Tujuan penelitian ini adalah mengevaluasi pengaruh perbedaan cahaya lampu pijar dengan perlakuan lama paparan 24 jam, 12 jam, dan tanpa cahaya. Rancangan Acak Lengkap dengan 3 perlakuan dan 3 ulangan digunakan dalam penelitian ini. Peubah yang diamati terdiri atas angka mortalitas, pertambahan bobot badan populasi, dan konversi media hidup dan pakan menjadi vermikompos. Hasil dari penelitian ini membuktikan bahwa perlakuan paparan cahaya 24 jam menunjukkan nilai peubah cacing tanah yang lebih tinggi dari perlakuan 12 jam dan lebih rendah dari kontrol tanpa paparan cahaya. Seluruh perlakuan tidak berpengaruh nyata terhadap konversi bobot media. Dalam pemeliharaan metode paling optimal menggunakan cahaya lampu selama 24 jam, dengan nilai lux cahaya yang lebih rendah dari 60 lux., Earthworm is one of the prospective animals which have enormous potential as supporting livestock in integrated farming system. Lumbricus rubellus is a relatifly small worm with approximate length of 4-6 cm and red brown or red-violet in terms of color. This animal fed on organic matters within the soil and proceed to decomposting organic matter. Microorganism’s diversity in a place are decided by several factors such as temperature, humidity, and exposure of light. The purpose in this study was to investigate the influence of different light exposure period of 24 hours, 12 hours, and without light exposure. The results shown by this study revealed that 24 hours light exposure treatment has better results on earthworm productivity, although not exceeding the control treatment’s result (no light exposure). Complete Randomization Design used as experiment design in this study. All treatment did not have real influnces to medium’s weight conversion rate. The most optimal method of utilising light would be 24 hours of exposure with lux rate lower than 60 lux.
Keyword: Dekomposisi, Lumbricus rubellus, Mikroorganisme, Paparan cahaya, Produktivitas

Judul: The Effect of Different Light Colour of Lamp on  The Productivity of Earth Worms.
Abstrak: Cacing tanah adalah salah satu inevertebrata yang banyak terdistribusi di seluruh dunia, dan menyukai tanah lembab yang kaya akan bahan organik. Lumbricus rubellus adalah spesies cacing tanah yang bersifat nokturnal, dan aktif pada malam hari. Warna lampu memiliki efek pada tanaman dan hewan lainnya. Tujuan penelitian ini adalah untuk menganalisis produktivitas Lumbricus rubellus dibawah pengaruh warna cahaya yang berbeda. Penelitian ini menggunakan tiga warna lampu berbeda yaitu merah, kuning, dan biru, serta kontrol, dengan keadaan lingkungannya disimpan dalam keadaan gelap. Parameter yang di ukur adalah pertambahan bobot badan, jumlah segmen, jumlah kokon dan berat media akhir. Hasil dari penelitian ini menunjukan bahwa warna lampu berpengaruh nyata dengan nilai (P<0,05) terhadap pertambahan bobot badan, produksi kokon, dan jumlah segmen. Cacing tanah dibawah lampu merah memiliki pertambahan bobot badan (15,08 g), produksi kokon (11,99), dan jumlah segmen (30,01) yang paling tinggi dibandingkan perlakuan lainnya, sedangkan cacing tanah dibawah lampu warna kuning menunjukan penambahan bobot badan (2,00 g/minggu), produksi kokon (2,24), dan jumlah segmen (28,67) yang paling rendah, Earthworm is one of the invertebrates which is distributed around the world, and preferred moist soil that is rich in organic matter. Lumbricus rubellus is a species of an earthworm that have nocturnal trait, and become active at night. Light color has also an effect on plant, and other animals. The purpose of this research was to observe Lumbricus rubellus productivity under the effect of different light colours. This research uses three different colour of lights, red, yellow and blue colour, with control, where the environment is being keep completely in dark. The parameters oberserved are weight gain, number of segments, number of cocoons from Lumbricus rubellus, and final media weight. Results from this study shows that colour of light have a real effect with value of (P<0,05) on weight gain, cocoon production, and total segment. Earthworm under red light have the highest weight gain (15,08 g), cocoon production (11,99), and total segment (30,01) compared to other treatment, while earthworm under the yellow light shows the lowest weight ii gain (2,00 g/week), cocoon production (2,24), and total segment (28,67) compared to other treatment.
Keyword: light colours, Lumbricus rubellus, productivity

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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