Judul: Kajian Model Hidden Markov Diskret dan Aplikasinya pada Harga Gabah Kering Panen
Abstrak: A discrete hidden Markov model is a model which consists of the cause of event and observations process. This model assumes that the cause of event is Markov chain which is not observed directly. The observations process has discrete-range. Parameters of this model are transition probabilities and expectation of observations process. They are estimated by using the maximum likelihood method and expectation maximization algorithm. The estimation procedure involves change of measure. The estimation of parameters uses Mathematica 6.0, a functional programming based algebraic computer systems. The model is then applied to the price of harvest dry rice from January 2000 until March 2007. The estimated parameters are used to calculate expectation of harvest dry rice price. The result of this study shows that the discrete hidden Markov model can be applied to model the harvest dry rice price.
Keyword: Markov chain, Discrete hidden markov model, Expectation maximization algorithm

Judul: The Study of Continuous Hidden Markov Model and Its Application on Harvest Dry Rice Price.
Abstrak: Continuous hidden Markov model (Elliot et al. 1995) is a model that consists of the cause of event and observations process. This model assumes that the cause of event is a Markov chain which is not observed directly, and the observations have continuous-range. Parameters of this model are transition probabilities, expectation and variance of observation process. They are estimated by using the maximum likelihood method and expectation maximization algorithm that involves the change of measure. Model parameters were estimated by using Mathematica 6.0 a functional program based computer algebra systems. The model was applied on price change of harvest dry rice in 2000 until 2007. The estimated parameters were used to calculate the expectation value of harvest dry rice price. The result of this study showed that the continuous hidden Markov model could be applied on harvest dry rice price., Proses Markov merupakan proses stokastik dengan sifat bahwa perilaku stokastik di masa yang akan datang hanya bergantung pada perilaku masa sekarang. Setiap kejadian berkaitan erat dengan penyebab kejadian tersebut. Jika penyebab kejadian tersebut tidak diamati secara langsung dan membentuk rantai Markov maka pasangan kejadian dan penyebabnya dapat dimodelkan dengan model hidden Markov (HMM). Misalkan X = {Xk;k e N}adalah rantai Markov yang bersifat homogen dan tidak diamati secara langsung, sedangkan Y = {~;k e N} adalah proses observasinya. Pasangan {(Xk'~)} merupakan model hidden Markov
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Judul: Hydroxyapatite-Chitosan Composite Coating on Stainless Steel 316 to Improve Corrosion Resistance
Abstrak: Metals that were used in bone implantation should have good corrosion resistance that were not easily corroded when implanted into the body. Metal corrosion resistance of stainless steel 316 can be enhanced through the metal coating by hydroxyapatite-chitosan composite with composition ratio of hydroxyapatite (gram) and chitosan 3% (mL) 0.2:0, 0.2:0.1, 0.2:0.5, 0.2:1.0, and 0.2:1.5. Besides improving the corrosion resistance of metal, the presence of chitosan also maintain the position of hydroxyapatite on metal surfaces. Corrosion resistance increases with increasing amount of chitosan added and the best composition of hydroxyapatite-chitosan composite was 0.2:1.0.
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