Judul: Model mangsa-pemangsa-parasit dengan pemanenan sebagai control terhadap penyakit
Abstrak: Predator-prey interaction in presence of parasite can change the system stability in the population. This study aims to analyze the stability of predator-prey-parasite model with harvesting as a disease control measure and to study the effects of decreasing or increasing the harvesting process to the disease. Predator-prey-parasite with harvesting model is applied to a system with shrimp Penaeidae sp population as prey, Whitespot disease as disease, and blekok birds as predator in estuary waters. Mathematica software is used to carry out some numerical simulations. The results from this study show that harvesting can be used as a tool for controlling disease by choosing certain harvesting way.
Keyword: 

Judul: Dinamika Solusi Model Mangsa Pemangsa dengan Pemangsa Menderita Dua Jenis Penyakit
Abstrak: Dalam penelitian ini, dianalisis kestabilan model mangsa pemangsa dengan melibatkan model penyebaran penyakit SIS (Susceptible Infected Susceptible) dan SI (Susceptible Infected) pada spesies pemangsa. Populasi yang terlibat dalam penelitian ini terdiri dari populasi mangsa, populasi pemangsa rentan, populasi pemangsa terinfeksi penyakit pertama, dan populasi pemangsa terinfeksi penyakit kedua. Dalam model ini diperoleh sebelas titik tetap. Analisis kestabilan titik tetap dilakukan dengan metode nilai eigen dan fungsi Lyapunov. Parameter yang digunakan untuk melihat dinamika populasi mangsa dan pemangsa adalah tingkat infeksi melalui kontak dengan pemangsa terinfeksi penyakit pertama dan kedua. Jika tingkat infeksi melalui kontak dengan pemangsa terinfeksi penyakit pertama diturunkan, maka populasi pemangsa terinfeksi penyakit pertama menuju kepunahan sehingga penyakit pertama pada pemangsa akan hilang. Jika tingkat infeksi melalui kontak dengan pemangsa terinfeksi penyakit kedua diturunkan, maka populasi pemangsa terinfeksi penyakit kedua menuju kepunahan sehingga penyakit kedua pada pemangsa akan hilang., In this study, stability of predator prey models was analyzed by involving the spread of SIS (Susceptible Infected Susceptible) and SI (Susceptible Infected) disease model in predator species. In this study, a population consists of prey and susceptible predator subpopulation, as well as predator subpopulation that infected by first and second disease. In this model eleven fixed point were obtained. Stability analysis of fixed point was carried out by eigen value method and Lyapunov function. The parameters to see the dynamics of prey and predator population are infection rates through contact with predators, which are that infected by first and second disease. If infection rates through contact with predator that infected by first disease is decreased, the predator population that infected by first disease goes to extinction, so that the first disease in the predator will disappear. If infection rates through contact with predator that infected by second disease is decreased, the predator population that infected by second disease goes to extinction, so that second disease in the predator will disappear.
Keyword: prey-predator, stability analysis, Lyapunov function, SIS epidemic model, SI epidemic model

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