Judul: Stability Analysis of Predator-Prey Model of Leslie-Gower with Allee Effect and Hunting Cooperation
Abstrak: Model dalam penelitian ini adalah model mangsa-pemangsa Leslie-Gower dengan mempertimbangkan adanya efek Allee pada populasi mangsa dan kerja sama perburuan pada populasi pemangsa. Tujuan dari penelitian ini adalah mengkaji pengaruh koefisien kerja sama perburuan dan tingkat efek Allee pada model. Metode yang digunakan adalah dengan mencari serta menganalisis kestabilan dari titik tetap dan melakukan simulasi numerik, serta menunjukkan keberadaan bifurkasi Hopf. Model ini memiliki empat titik tetap dengan sifat kestabilannya dipengaruhi oleh nilai parameter. Peningkatan nilai tingkat efek Allee mengakibatkan populasi mangsa-pemangsa mengalami kepunahan. Penurunan nilai tingkat efek Allee mengakibatkan kedua populasi dapat hidup berdampingan (koeksistensi) dan terhindar dari kepunahan. Perubahan nilai koefisien kerja sama perburuan mengakibatkan kedua populasi koeksistensi. Terdapat titik tetap yang berhubungan dengan perubahan sifat kestabilan dan munculnya siklus limit, yang menandai terjadinya bifurkasi Hopf., The model in this study is the Leslie-Gower predator-prey model by considering the Allee effect in the prey population and hunting cooperation in the predator population. The purpose of this study is to examine the effect of hunting cooperation coefficient and the level of Allee effect on the model. The method used is to find and analyze the stability of the fixed point and perform numerical simulations, and show the existence of Hopf bifurcation. The model has four fixed points with stability properties influenced by parameter values. An increase in the value of the Allee effect level results in the extinction of the predator-prey population. A decrease in the value of the Allee effect level results in both populations being able to coexist and avoid extinction. A change in the value of the coefficient of hunting cooperation results in the coexistence of the two populations. There are fixed points that related with the changes in stability properties and the emergence of limit cycles, which indicate the occurrence of Hopf bifurcation.
Keyword: Allee effect, Hopf bifurcation, hunting cooperation, Leslie-Gower, predator-prey

Judul: Analisis Model Mangsa-Pemangsa Leslie-Gower dengan Adanya Faktor Ketakutan dan Perlindungan Mangsa
Abstrak: Dalam tulisan ini dipelajari model mangsa-pemangsa Leslie-Gower dengan adanya faktor ketakutan dan perlindungan mangsa yang dikembangkan oleh Wang et al. (2019). Dari model ini, terdapat empat titik tetap. Kestabilan titik tetap pertama bersifat simpul takstabil, kestabilan titik tetap kedua bersifat sadel, titik tetap ketiga dapat bersifat sadel atau simpul stabil, dan titik tetap keempat dapat bersifat spiral takstabil, spiral stabil, sadel, atau simpul stabil bergantung nilai parameter faktor ketakutan dan perlindungan mangsa. Adanya faktor ketakutan dan perlindungan mangsa dapat mempengaruhi populasi mangsa pemangsa. Semakin besar tingkat faktor ketakutan, maka populasi akan stabil pada titik tetap E_2, populasi mangsa akan semakin menurun menuju kepunahan. Semakin besar tingkat perlindungan mangsa, maka populasi akan stabil pada titik tetap E_3, populasi mangsa akan semakin meningkat dan terhindar dari kepunahan. Bifurkasi Hopf terjadi pada titik tetap keempat, di mana terjadi perubahan kestabilan dari spiral takstabil menjadi spiral stabil yang berakibat munculnya limit cycle., In this manuscript a mathematical predator-prey model of Leslie-Gower with the fear factor and the prey refuge that was previously investigated by Wang et al. (2019) is studied. In this model, there are four fixed points. Stability of the first fixed point is unstable node, stability of the second fixed point is saddle, the third fixed point could be a saddle or stable node, and the fourth fixed point could be an unstable spiral, stable spiral, saddle or stable node depending on two parameters of the fear factor and the prey refuge. The existence of fear factor and the prey refuge can influence the predator-prey populations. As the level of fear factors increases, the population will be stable at the fixed point E_2, prey population will decline towards extinction. As the level of prey refuge increases, the population will be stable at the fixed point E_3, prey population increases and avoids extinction. Hopf bifurcation occurs on the fourth fixed point, where the unstable spiral changed into a stable spiral which results in the emergence of a limit cycle.
Keyword: Hopf Bifurcation, Fear factor, Leslie-Gower, predator-prey, prey refuge

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