Judul: Masalah Kontrol Optimum Hama Secara Hayati
Abstrak: Pests are species that can attack crops and interfere farming activity. Effort to reduce the effect of pests is necessary. It can be accomplished either by chemical control through insecticides or by biological control using natural enemy intervention. In this work, pest control effort is formulated by a mathematical model, i.e., an optimal pest control problem. The primary objective of this work is to determine control strategies which maintain the density of the pest population in the equilibrium level below economic losses. Two-step control strategy is proposed by using the combination of chemical and biological controls; in the first step to speed-up pest reduction, and solely by using the biological control in the second step to maintain the admissible level. The control strategy is then applied to a predator-prey model which involves Anticarsia gemmatalis as a pest to soybean and Geocoris sp. as a natural enemy. It shows that the admissible level of 20 pest/m2 can be attained and maintained subsequently.
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Judul: Biological Pest Control Strategies using Sterile Insect Technique and Natural Enemies
Abstrak: Indonesia adalah negara agraris sehingga pertanian memiliki peranan penting bagi Indonesia. Oleh sebab itu, masalah yang berkaitan dengan pertanian seperti serangan hama selalu menjadi topik yang penting pula. Pestisida kimia banyak digunakan dalam pengendalian hama ini, namun pestisida kimia memiliki banyak dampak negatif bagi lingkungan. Pengendalian Hama Terpadu (PHT) dikembangkan untuk mengurangi penggunaan pestisida kimia. Teknik dalam PHT yang digunakan pada karya ilmiah ini, yaitu SIT (Sterile Insect Technique) dan musuh alami. Dalam karya ilmiah ini, dilakukan pemodelan kontrol optimum untuk mengoptimalkan kepadatan populasi tanaman menggunakan strategi pelepasan serangga hama steril dan penambahan musuh alami ke area lahan tanaman sebagai variabel kontrolnya. Prinsip maksimum Pontryagin digunakan dalam penentuan syarat perlu optimalitas dan metode Runge-Kutta orde 4 serta backward-forward sweep method digunakan untuk mengetahui solusi numeriknya., Indonesia is an agricultural country, so agriculture has an important role for Indonesia. Therefore, problems related to agriculture, such as pests, always be an important topic. Chemical pesticides are highly used in controlling these pests, however chemical pesticides have lots of negative impacts on the environment. Integrated Pest Management (IPM) was developed to reduce the use of these chemical pesticides. There are techniques of IPM that are used in this paper, i.e. sterile insect technique (SIT) and natural enemies. In this paper, the optimum control modelling was carried out to optimize the density of the plant population using the strategy of releasing sterile insect pests and adding natural enemies to the crops area as control variables. Pontryagin’s maximum principle is used in determining the requirements for optimality, fourth-order Runge Kutta method and backward-forward sweep method are used to determine the numerical solution.
Keyword: optimal control, fourth-order Runge Kutta method, natural enemies, Pontryagin’s maximum principle, sterile insect technique

Judul: Characterizations of low alloy steel sae 4422  plated with chromic acid (Cro3)
Abstrak: Characterizations of low alloy steel SAE 4422 plated with chromic acid (CrOrO3) was use Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), RD),Energy Dispersive Analysis of X-Ray (EDAX), Hardness Test and Roughness Test. Microstructures analysis exhibits cracks and grain boundaries microcracks as a characteristics of chrome metal found at plating metal. Perlite and Ferrite as grains of steel found at base metal with grain boundaries around it. Phase analysis of plating metal appropriate to chrome metal with lattice constant (a) is 2.559 Å and phase analysis of base metal appropriate to iron ferrite with lattice constant (a) is 3.318 Å. Both plating and base metal have cubic system. Chemical analysis of plating metal at surface section exhibits that cracks area have highest value of carbon element compare with grains and grains boundaries area. While chemical analysis of base metal at cross section exhibits that perlite have highest value of carbon element compare with ferrite and grain boundaries. The hardness value of plating metal at surface section and cross section are 753 and 637 VHN. While, the hardness value of base metal and interface area at cross section are 205 and 373 VHN. The roughness value at measurement points of chrome surface for as received sample are 0.445 μm. Observation used Optical Microscopy and Scanning Electron Microscopy exhibits surface irregularities combine to form surface texture of plating metal at surface section.
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