Judul: Model Mangsa-Pemangsa Berhierarki
Abstrak: Pemodelan berbasis agen merupakan salah satu model terbaru dengan pengembangan yang praktis. Model mangsa-pemangsa merupakan model yang menunjukan hubungan jumlah populasi antara mangsa dan pemangsa di suatu ekosistem. Model mangsa-pemangsa dalam penelitian ini menggunakan pemodelan berbasis agen dengan meninjau perilaku dan interaksi hewan seperti di alam. Dengan menggunakan agent-based model ini, perilaku hewan dapat melihat kompleksitas serta menganalisisnya sesuai fenomena sebenarnya di alam. Penelitian ini bertujuan mendapatkan model mangsa-pemangsa berdasarkan pendekatan Agent-based Model dengan mempertimbangkan hierarki rantai makanan. Aturan yang digunakan yaitu tiap agen dapat berkembang biak dengan agen yang sama, agen dengan tingkat lebih tinggi dapat memakan agen dengan tingkat lebih rendah, agen dengan tingkat lebih rendah dapat melindungi diri, mati secara alami, dan mati akibat kelaparan. Penelitian ini dilakukan dengan empat skenario. Aturan yang telah ada kemudian divariasikan sesuai dengan skenario. Hasil simulasi yang terlihat memiliki hasil yang beragam. Pengorganisasian diri terjadi dapat terjadi pada setiap agen. Pengorganisasian diri dilakukan agar agen tetap bertahan hidup. Pengorganisasian dilakukan saat agen berhasil membuat kelompoknya sendiri. Entropi total sistem yang dihasilkan memiliki pola meningkat di awal kemudian turun dan berakhir dengan keadaan stabil. Berdasarkan hal tersebut, diketahui bahwa sistem mengalami kestabilan yang dapat terlihat pada agen yang berkumpul dengan agennya sendiri., Agent-based model is a new model with practical development. Prey-predator model is a model that is showing relation between prey and predator population in an ecosystem. In this research, agent-based model is used in prey-predator model by observing animal behavior and interaction in nature. Complexity of animal behavior can be seen and analyzed with agent-based model. This research aims to obtain a prey-prey model based on the Agent-based Model approach by considering the food chain hierarchy. Rules that are used in this model are each agent can breed with same kind, higher-level agent can eat lower-level agent, lower-level agent can protect themselves, die naturally, and die from starvation. This research was conducted with four scenarios. The existing rules are then varied according to the scenario. Simulation results that are shown have a lot of variation. Self-organization can happen to any agent. Self-organization is done so agent can survives. Self-organization take place when agents succeed in creating their own groups. The total entropy of every scenario are increasing at the beginning then drops and ends with stable state. Systems in this simulation experience stability which can be seen in agents that gather into their own.
Keyword: agent-based model, hierarchal prey-predator model

Judul: Analysis of Four Species Prey-Predator Model
Abstrak: Kompleksitas interaksi mangsa-pemangsa yang terjadi dalam suatu ekosistem dapat digambarkan ke dalam bentuk jaring-jaring makanan dengan memetakan jenis makanan yang dimakan oleh suatu organisme. Dalam karya ilmiah ini direkonstruksi model mangsa-pemangsa dengan empat spesies, terdiri dari dua mangsa, satu pemangsa tengah, dan satu pemangsa puncak. Dengan melakukan simulasi numerik, didapatkan tiga belas titik tetap dengan jenis kestabilan yang beragam. Simulasi numerik juga dilakukan untuk melihat pengaruh perubahan nilai laju pertumbuhan kedua mangsa terhadap populasi mangsa dan pemangsa. Dengan batas nilai tertentu, peningkatan laju pertumbuhan kedua mangsa akan mengatasi kepunahan setiap populasi, baik populasi mangsa maupun pemangsa dalam suatu sistem tertentu. Untuk beberapa kasus, titik tetap mengalami perubahan sifat kestabilan dari spiral stabil menjadi spiral tak stabil. Perubahan kestabilan pada titik tetap menyebabkan terbentuknya siklus limit yang mengindikasikan terjadinya bifurkasi Hopf pada kasus tersebut., The complexity of prey-predator interactions that occur in an ecosystem can be described in the form of food webs by mapping the type of food consumed by an organism. This scientific research reconstructed prey-predator models with four species, consisting of two preys, one middle predator, and one apex predator. By performing numerical simulations, thirteen fixed points with various types of stability were obtained. Numerical simulations were also carried out to observe the effect of changes in the growth rate values of both preys on prey-predator populations. With a certain value limit, an increase in the growth rate of both preys can resolve the extinction of each population, both prey and predator populations in an ecosystem. For several cases, the fixed point changes its stability properties from a stable spiral to an unstable spiral. The changes of stability properties at fixed points cause the formation of a limit cycle that indicates the occurrence of Hopf bifurcation.
Keyword: food webs, four species, limit cycle, prey-predator, stability

Judul: Enhancement of photon absorbtion on BaxSr1-xTiO3 thin films semiconductor using photonic crystals.
Abstrak: In this research, has been conducted BaxSr1-xTiO3 (BST) thin films manufacturing for mole fraction x = 0.25, 0.35, 0.45, and 0.55; and concentration of 1 molar using chemical solution depositon (CSD) method. The materials, which are used in this research, are barium acetate [Ba(CH3COO)2, 99%], strontium acetate [Sr(CH3COO)2, 99%], titanium isopropoxide [Ti(C12O4H28), 97.999%], gallium trioxide [Ga2O3], 2-methoxyethanol [H3COOCH2CH2OH, 99%] and 1 x 1 cm of transparent conductive oxide (TCO) glass as substrate. Two BST thin films are made that for BST thin films which are doped by 10% galium (BGST) as p-type layer and pure BST solution as n-type. BST solution is made by reacting barium acetate [Ba(CH3COO)2, 99%], strontium acetate [Sr(CH3COO)2, 99%] and titanium isopropoxide [Ti(C12O4H28)] into 2-methoxyethanol solvent [H3COOCH2CH2OH, 99%] in accordance with mass gram for each x value. While, BGST solution is made in the same way as BST solution, plus adding gallium at 10% of the mass of BST. Once all materials are reacted, then vibrated using ultrasonic for 90 minutes, and followed by coating BGST / BST on the TCO substrate. Once the layer is formed, then annealed for 15 hours at temperature of 500 °C with increasing rate of 1.67 oC/minute. Characterizations of BST thin films with or without photonic crystals include the absorbance and transmittance in the visible light spectrum, as well as the electrical photoconductivity characterizations. From BST thin films without photonic crystals indicate that our thin films have light absorption area on almost the entire range of the visible light spectrum even to the infrared range with absorption value over than 67.6%, in addition, it can be seen that the maximum absorbance of BST thin films for all mole fractions lie in blue to green light spectrum region, 457 nm ≤ λ ≤ 570 nm and the minimum in yellow to red light spectrum region, 570 nm ≤ λ ≤ 678 nm. The largest absorbance is found at x = 0.25 with average absorbance value of 92.04% and maximum and minimum absorbance peaks at wavelength of 500.89 and 657.72 nm, respectively. At x = 0.35, average absorbance value decreased to 83.55% with maximum and minimum peaks at 505.73 and 613.68 nm, respectively. Then increased to 91.16% at x = 0.45 with maximum and minimum peaks at 506.04 and 618.56 nm, respectively. At x = 0.55, average absorbance value decreased to 80.12% with maximum and minimum peaks at 507.85 and 608.79 nm, respectively. Moreover, it can be seen that the addition of barium mole fraction leads to wider maximum absorbance or minimum transmittance peaks and narrower minimum absorbance or maximum transmittance peaks in the same range of the green and blue & red light spectrums, respectively. BST thin films with photonic crystals show increasing in absorption for all x values in the range of 3.04 into 13.33%. At x = 0.25, average absorbance percentage increased 3.96% from 92.4 into 95.68%, for x = 0.35 average percentage increased 7.07% into 89.45 from 83.55%. Furthermore, average absorbance of BST thin films at x = 0.45 increased 3.04% from 91.16 into 93.93% and x = 0.55 has
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