Judul: The Effect of Improvement of Folding Traps Entrance Construction and Choice of Bait on Freshwater Lobster Catches
Abstrak: Bubu payung merupakan salah satu jenis bubu lipat yang banyak dioperasikan di Belitung Timur. Penggunaannya difokuskan pada penangkapan lobster air tawar. Bubu payung standar memiliki kekurangan yaitu sulit dimasuki lobster. Lobster yang telah terperangkap juga mudah keluar dari pintu masuk, sehingga bubu standar tidak efektif untuk menangkap lobster air tawar. Salah satu upaya yang dilakukan untuk mengoptimalkan bubu adalah dengan memperbaiki konstruksi pintu masuk agar lobster mudah memasuki bubu dan sulit ketika meloloskan diri. Konstruksi pintu bubu payung yang tepat telah diperoleh dari hasil laboratorium, namun pengujian lapang belum dilakukan. Tujuan penelitian adalah menentukan umpan yang tepat, menentukan komposisi hasil tangkapan bubu payung standar dan modifikasi, membuktikan bahwa bubu payung modifikasi mampu meningkatkan hasil tangkapan serta memperoleh waktu pengoperasian bubu yang tepat. Tahap pengujian umpan dilakukan di laboratorium, sedangkan pengujian bubu di lakukan di lapang. Hasil uji umpan didapatkan lobster memilih lemuru busuk (36jam) sebanyak 73 kali dan betutu busuk (36 jam)(27 kali). Bubu payung standar dan modifikasi memerangkap sebanyak 1.706 lobster seberat 61.610,5 g, kemuring (228 ekor; 400 g), dan ban (14 ekor; 85 g). Bubu payung modifikasi mampu memerangkap lobster sebanyak 1.360 lobster, atau 3,93 kali lebih banyak dibandingkan dengan bubu payung standar (346 lobster). Berat lobster yang terperangkap oleh bubu payung modifikasi seberat 48.250 g, atau 3,61 kali lebih tinggi daripada bubu payung standar (13.360,5 g). Pengoperasian bubu di pukul 18.00-21.00 WIB memiliki hasil tangkapan yang paling banyak dibandingkan dengan waktu lainnya., Umbrella trap is one type of folding trap that is widely operated in East Belitung. Its use is focused on catching freshwater lobster. Standard umbrella traps have the disadvantage of being difficult for lobsters to enter. Lobsters that have been trapped are also easy to escape from the entrance, so standard traps are ineffective for catching lobster. One of the efforts made to optimize the trap is to improve the construction of the entrance so that the lobsters are easy to enter the trap and difficult to escape. The correct construction of the umbrella trap door has been obtained from laboratory results, but field testing has not been carried out. The objectives of the study were to determine the right bait, determine the composition of the catch of standard and modified umbrella traps, prove that modified umbrella traps were able to increase the catch and obtain the correct operating time of the trap. The bait testing phase is carried out in the laboratory, while the trap testing is carried out in the field. The bait test results showed that lobsters chose rotten lemuru (36 hours) 73 times and rotten betutu (36 hours) (27 times). Standard and modified umbrella traps trapped 1,706 lobsters weighing 61,610.5 g, kemuring (228 fish; 400 g), and tires (14 tails; 85 g). The modified umbrella trap was able to trap 1,360 lobsters, or 3.93 times more than the standard umbrella trap (346 lobsters). The weight of the lobster trapped by the modified umbrella trap weighed 48,250 g, or 3.61 times higher than the standard umbrella trap (13,360.5 g). The trap operation at 18.00-21.00 WIB has the highest catches compared to other times.
Keyword: Bubu payung, hasil tangkap sampingan, lobster air tawar, umpan

Judul: Construction Improvement of Folding Traps for Catching Freswater Crayfish (Cherax sp.)
Abstrak: Cherax quadricarinatus merupakan salah satu jenis lobster air tawar yang memiliki nilai ekonomis tinggi. Salah satu daerah penyebarannya Belitung Timur. Masyarakat Belitung Timur melakukan penangkapan lobster air tawar menggunakan bubu payung. Bubu payung standar memiliki kekurangan yaitu sulit dimasuki lobster. Lobster yang telah terperangkap juga mudah keluar dari pintu masuk, sehingga bubu standar tidak efektif untuk menangkap lobster air tawar. Salah satu upaya yang dilakukan untuk mengoptimalkan bubu adalah dengan memperbaiki konstruksi pintu masuk agar lobster mudah memasuki bubu dan sulit ketika melepaskan diri. Tujuan penelitian ini adalah menentukan umpan yang tepat untuk bubu, menentukan konstruksi pintu yang tepat dan membandingkan hasil tangkapan antara bubu pintu standar dengan pintu modifikasi. Seluruh penelitian dilakukan pada skala laboratorium. Penelitian menggunakan akuarium dan kolam pembesaran. Uji konstruksi pintu bubu dilakukan di akuarium sedangkan uji makanan dan uji bubu dilakukan di kolam pembesaran. Konstruksi pintu bubu yang tepat adalah memiliki pintu luar menyentuh dasar bubu, sudut lintasan 40˚ dan bentuk pintu bagian dalamnya persegi panjang. Bubu modifikasi mampu memerangkap lobster sebanyak 76,92%, sedangkan bubu standar sebanyak 23,08%. Bubu standar mampu meloloskan lobster sebanyak 78,79%, sedangkan bubu modifikasi hanya sebanyak 21,31%. Umpan yang tepat digunakan adalah ikan laisi (lemuru)., Cherax quadricarinatus is one type of freshwater crayfish that has high economic value. One of the distribution areas is East Belitung. The people of East Belitung catch freshwater crayfish using umbrella traps. Standard umbrella traps have the disadvantage that it is difficult for lobsters to enter. Lobsters that have been trapped are also easy to escape from the entrance, so standard traps are ineffective for catching crayfish. One of the efforts made to optimize the trap is to improve the construction of the entrance so that the lobsters are easy to enter the trap and difficult to escape. The purpose of this study was to determine the right bait for the trap, determine the right door construction and compare the catch between the standard door trap and the modified door. All research was conducted on a laboratory scale. Research using aquariums and rearing ponds. The trap door construction test was carried out in the aquarium while the food test and trap test were carried out in a rearing pond. The proper construction of a trap door is to have the outer door touch the bottom of the trap, the angle of passage is 40˚ , and the shape of the inner door is rectangular. The modified trap was able to trap lobster as much as 76.92%, while the standard trap was 23.08%. Standard traps were able to pass lobster as much as 78.79%, while modified traps were only 21.31%. The right bait to use is laisi fish (lemuru).
Keyword: bait, freshwater crayfish, umbrella 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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