Judul: Folding Trap Door Construction Modification for Blue  Swimming Crab (Portunus sp.)
Abstrak: Produksi rajungan di PPN Karangantu cenderung menurun. Hal ini menunjukkan bahwa alat tangkap yang digunakan yakni bubu belum efektif, sehingga diperlukan modifikasi. Modifikasi yang dilakukan yaitu menghilangkan bentuk funnel dan diganti dengan pintu satu arah pada mulut bubu, sehingga tujuan dari penelitian ini adalah membandingkan respons dan tingkah laku rajungan terhadap bubu kontrol dan bubu modifikasi, terdiri dari pola pergerakan mendekati bubu serta waktu yang dibutuhkan untuk menemukan pintu bubu dan memasuki bubu. Metode yang digunakan pada penelitian ini adalah percobaan laboratorium. Hasil penelitian yang didapatkan yaitu pola pergerakan rajungan pada bubu modifikasi umumnya melalui bagian tengah pintu sedangkan pada bubu kontrol melalui bagian sisi funnel. Pola pergerakan memengaruhi waktu yang dibutuhkan rajungan untuk menemukan pintu dan memasuki bubu. Perbedaan waktu yang dibutuhkan rajungan dalam menemukan pintu bubu kontrol dan modifikasi menunjukkan perbedaan yang signifikan, namun waktu rajungan memasuki bubu tidak menunjukkan adanya perbedaan yang signifikan antara kedua jenis bubu, The production of blue swimming crab in Karangantu Archipelago Fishing Port tends to decrease. This indicates that the fishing gear used, namely the trap, is not effective, thus requiring modification. The modification involves removing the funnel-shaped entrance and replacing it with a one-way door at the mouth of the trap. The purpose of this study is to compare the responses and behavior of crabs towards the control trap and the modified trap, specifically examining their approach patterns towards the trap and the time taken to find and enter the trap. The method used for this research is a laboratory experiment. The results show that the movement pattern of crabs towards the modified trap mostly occurs through the center of the door, while for the control trap, it occurs through the sides of the funnel. The movement pattern affects the time taken by crabs to find the trap's door and enter it. There’s a significant difference in the time taken by crabs to find the door between the control and modified traps. However, there’s no significant difference in the time taken by crabs to enter the traps between the two types.
Keyword: funnel, pintu satu arah, Portunus sp., one-way door

Judul: The Effect of Mechanical Door Modifications on Folding  Traps on Blue Swimming Crab Behavior
Abstrak: Kualitas dan kuantitas hasil tangkapan bubu rajungan dipengaruhi oleh konstruksi yang digunakan. Upaya untuk meningkatkan produktivitas bubu dapat dilakukan dengan memodifikasi bagian slope net. Tujuan dari penelitian ini yaitu mengidentifikasi tingkah laku serta membandingkan waktu yang dibutuhkan rajungan dalam menemukan pintu hingga masuk ke dalam bubu modifikasi dan bubu kontrol. Penelitian ini dilakukan menggunakan metode eksperimental di Laboratorium Hatchery AUP Banten. Data hasil penelitian dianalisis menggunakan analisis deskriptif dan statistik. Hasil penelitian menunjukkan terdapat delapan pola yang dibentuk rajungan untuk masuk ke dalam bubu modifikasi dengan pola terbanyak (22%) yaitu M5 (mendekati dari sisi kanan dan masuk melalui bagian tengah) dan lima pola untuk bubu kontrol dengan pola terbanyak (28%) yaitu K3 (mendekati bagian tengah bubu dan masuk melalui kiri pintu). Sedangkan waktu yang dibutuhkan rajungan dalam menemukan pintu bubu modifikasi dan kontrol tidak berbeda signifikan dengan masing-masing 102,1 detik dan 136 detik, dengan standard error (Se) sebesar 4,53 dan 4,52. Akan tetapi memiliki perbedaan yang signifikan untuk waktu yang dibutuhkan rajungan masuk ke dalam bubu dengan masing-masing 27,6 detik dan 47,05 detik, dengan standard error (Se) sebesar 13,3719 dan 20,7338., The quality and quantity of crab trawl catches are influenced by the construction used. Increasing the productivity of the traps can be done by modifying the slope part of the slope net. The purpose of this study was to identify the behavior and compare the time required by the crab in finding the door to enter the modified trap and control trap. This research was conducted using an experimental method at the AUP Banten Hatchery Laboratory. The data were analyzed using descriptive and statistical analysis. The results showed that there were eight patterns formed by crabs to enter the modified trap with the most patterns (22%) namely M5 (approaching from the right side and entering through the center) and five patterns for the control trap with the most patterns (28%) namely K3 (approaching the center of the traps and entering through the left door). Meanwhile, the time taken by crabs in finding the door of the modified and control trap was not significantly different with 102.1 seconds and 136 seconds respectively, with a standard error (Se) of 4.53 and 4.52. However, there is a significant difference in the time taken by the crab to enter the trap with 27.6 seconds and 47.05 seconds respectively, with a standard error (Se) of 13.3719 and 20.7338.
Keyword: behavior, blue swimming crab, funnel, folding traps, mechanical door, modification

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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