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: Performa Cacing Tanah (Lumbricus rubellus) Terhadap Warna Cahaya Lampu Yang Berbeda
Abstrak: Cacing tanah merupakan hewan invertebrata yang tersebar di seluruh dunia dan memiliki beragam manfaat. Salah satu jenis cacing tanah yang banyak dibudidayakan yaitu Lumbricus rubellus. Cacing ini merupakan hewan nokturnal yang bersifat fototaksis negartif. Warna cahaya lampu diduga berpengaruh terhadap performa cacing tanah. Penelitian ini bertujuan menganalisis performa Lumbricus rubellus dengan pengaruh warna cahaya lampu yang berbeda. Penelitian ini menggunakan tiga warna lampu yang berbeda yaitu jingga, hijau, ungu, serta gelap sebagai kontrol. Peubah yang diamati adalah pertambahan bobot, bobot media, jumlah segmen sampai klitelum, jumlah kokon, pH media dan jumlah populasi. Hasil penelitian menunjukkan bahwa ketiga jenis warna tidak dapat meningkatkan performa cacing tanah Lumbricus rubellus secara signifikan. Meskipun warna hijau dan ungu dapat meningkatkan pertambahan bobot badan namun nilainya masih lebih kecil daripada kondisi gelap., Earthworms are invertebrate animals that are spread throughout the world and have various benefits. One type of earthworm that is widely cultivated is Lumbricus rubellus. This worm is a nocturnal animal with negative phototaxis. The color of the lamp light is thought to have an effect on the performance of earthworms. This study aims to analyze the performance of Lumbricus rubellus with the influence of different light colors. This study used three different light colors, orange, green, purple, and dark as a control. The observed variables were weight gain, media weight, number of segments to the clitelum, number of cocoons, media pH and total population. The results showed that the three types of color did not significantly improve the performance of the earthworm Lumbricus rubellus. Although green and purple can increase body weight gain, the value is still smaller than the dark conditions.
Keyword: Light colours, Performance, Lumbricus rubellus

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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