Judul: Analisis Kestabilan Model Mangsa-Pemangsa dengan Interferensi Antarpemangsa
Abstrak: In this study we reconstructed a predator-prey model of three animal species in a food chain, which consist of two species of predator and one species of prey (Feng et al. (2010)). From this model we investigated the effects of interference between predators based on the saturation and competition levels. In the stability analysis five equilibrium points obtained, in which two of them are unstable saddles. The effects of saturation and competition levels to population dynamics is shown by using numerical approach, where four conditions are considered. In the first condition, the saturation level of two predators is bigger than the competition level. In the second condition, the saturation level of two predators is lower than the competition level. In the third condition, the saturation level of predator I is bigger than its competition level, but saturation level of predator II is lower than its competition level. The fourth condition, the saturation level of predator I is lower than its competition level, but saturation level of predator II is bigger than its competition level. In general, the simulation results of the four conditions above, concluded that the saturation level of predator I and competition level of predator II effects the stability of populations, whereas saturation level of predator II and competition level of predator I did not effects the stability of populations.
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Judul: Analisis kestabilan model interaksi dua pemangsa-satu mangsa
Abstrak: Interaksi antar makhluk hidup dalam kehidupan ini ada yang berdampak positif, negatif dan ada pula yang tidak berpengaruh terhadap makhluk hidup lain. Tulisan ini akan membahas model interaksi antara dua pemangsa dengan satu mangsa yang didasari dari model mangsa-pemangsa Lotka-Volterra. Pada model yang dikembangkan ini diasumsikan bahwa interaksi antar pemangsa bersifat komensalis, artinya interaksi dimana satu spesies pemangsa memperoleh keuntungan, sedangkan spesies pemangsa lainnya tidak terpengaruh. Model yang disusun ini terdiri atas variabel-variabel R (banyaknya mangsa), H (banyaknya pemangsa inang), C (banyaknya pemangsa yang komensalis terhadap H), u (tingkat pertumbuhan mangsa), v (tingkat pemangsaan pemangsa C), w (tingkat pemangsaan pemangsa H), 0 ( efisiensi konversi C), p ( efisiensi konversi H), x (tingkat kematian pemangsa C), dan y (tingkat kematian pemangsa H). Kestabilan model interaksi dua pemangsa-satu mangsa ini diperoleh dari kriteria Routh-Hurwitz. Pada kriteria ini, pengujian kestabilan dilakukan di sekitar titik-titik tetap yang diperoleh dari model tersebut. Hasil yang diperoleh menunjukkan bahwa, jika populasi pemangsa inang punah, maka akan terjadi ketidakstabilan, sedangkan jika tingkat kematian pemangsa C lebih besar atau sama dengan tingkat kematian pemangsa H, maka akan menyebabkan kestabilan. Pada kondisi ini, jika tingkat kematian salah satu pemangsa meningkat, maka populasi pemangsa tersebut turun, dan populasi pemangsa yang lain naik.
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Judul: Elektrodeposisi Film Tipis Semikonduktor Cu2ZnSnS4 (CZTS) pada Substrat Kaca ITO
Abstrak: Semiconductor Cu2ZnSnS4 (CZTS) thin film that can be used as absorber layers on solar cell module was made via electrodeposition method. CZTS thin film was electrodeposited on the surface of a silicate glass coated with a thin layer of indium tin oxide (ITO). Deposition process was done using potentiostatic mode at room temperature with a potential of 1.05 V for 30, 45, and 60 minutes, followed with annealing the film at 2 different temperatures, 500 ºC using furnace and 180 ºC using hot plate, both treatments for 45 minutes in N2/H2S atmosphere. The X-ray difractograms were analyzed using Match 2 program and showed that the CZTS thin films had kesterit crystalline structure, with a low percentage of CZTS phase. The thin film also contained secondary phases such as Cu2S, ZnS, and SnS. The obtained CZTS thin films had a thickness between 1.039 and 1.676 μm. Absorption study showed that the band gap energy of CZTS thin films which was annealed using furnace ranged from 1.50 to 1.52 eV, whereas that annealed using the hot plate was not observed. The band gap energy value showed that CZTS thin films can be used as sunlight absorber layers on solar cell. The formation of CZTS crystal film on this investigation was effectively performed using furnace annealing process at a temperature of 500 ºC with deposition time of 45 minutes.
Keyword: Thin film, Electrodeposition, Cu2ZnSnS4