Judul: Kajian Model Hidden Markov Kontinu dan Aplikasinya pada Harga Beras
Abstrak: Continuous hidden Markov model with discrete time (Elliot et al. 1995) is a model consists of the cause of event and observation process. This model assumes that the cause of event is a Markov chain in discrete time, observed indirectly. The observation process has continuous range and future observation is influenced by the cause of present event. Parameters of this model are transition probability matrices of the cause of event, vector and vector 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 7.0 functional programming computer algebra systems. The model is then applied to the price change of rice from February 2004 until May 2009. The estimated parameters are used to calculate the expectation value of rice price. As a result, this research convinces that the hidden Markov model can be applied to the price of rice.
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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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