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: Analysis of Predator-Prey Model of Holling  Type II with the Fear Factor and Allee Effect on Prey
Abstrak: Dalam tulisan ini dianalisis model Holling tipe II dengan adanya faktor ketakutan dan efek Allee pada mangsa. Penelitian ini bertujuan untuk menganalisis pengaruh faktor ketakutan serta efek Allee pada mangsa terhadap dinamika populasi model. Langkah yang dilakukan adalah dengan merekonstruksi model, menganalisis kestabilan titik tetap, mencari keberadaan bifurkasi Hopf serta melakukan simulasi numerik untuk menunjukkan kesesuaian analisis dengan solusi numeriknya. Model ini memiliki lima titik tetap yang stabilitasnya bergantung pada pemilihan nilai parameter. Simulasi numerik dilakukan dengan bantuan software Wolfram Mathematica 12.1 dengan melakukan perubahan terhadap nilai parameter efek Allee dan faktor ketakutan. Semakin kecil nilai parameter efek Allee mengakibatkan baik populasi mangsa maupun pemangsa dapat hidup berdampingan sehingga terhindar dari kepunahan. Semakin kecil nilai parameter faktor ketakutan mengakibatkan peningkatan pada populasi pemangsa, walaupun tidak berakibat pada kepunahan mangsa. Bifurkasi Hopf terjadi pada salah satu titik tetap, di mana terjadi perubahan kestabilan dari spiral stabil menjadi spiral tak stabil dan ditandai dengan munculnya limit cycle., This manuscript analyzes the Holling type II model in the presence of fear factor and the Allee effect on prey. This study aims to analyze the influence of the fear factor and the Allee effect on prey on the population dynamics of the model. The steps taken are to reconstruct themodel, to analyze the stability of the fixed point, to look for the existence of Hopf bifurcation and to perform numerical simulations to show the suitability of the analysiswith the numerical solution. The model has five fixed points whose stability depends on the selection of parameter values. Numerical simulations were carried out with the help of Wolfram Mathematica 12.1 software by changing the parameter values of the Alle effect and fear factor. The smaller the value of the Allee effect parameter results in both prey and predator populations being able to coexist so as to avoid extinction. The smaller the value of the fear factor parameter results an increase in the predator population, although it does not result in the extinction of the prey. Hopf bifurcation occurs at one of the fixed points, where there is a change in stability from a stable spiral to an unstable spiral and is characterized by the appearance of a limit cycle.
Keyword: Allee effect, fear factor, Holling type II, hopf bifurcation, predator-prey

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