Judul: Characterization os soils with low activity clay, and the effect of iron oxides on some soil properties
Abstrak: Tanah di Indonesia sebagian besar terdiri dari tanah merah yang telah terlapuk lanjut. Kebanyakan tanah tersebut didominasi liat aktivitas rendah sehingga dapat menimbulkan masalah bagi pertumbuhan tanaman. Salah satu komponen liat tersebut adalah besi oksida. Sehubungan dengan lahan subur banyak dikonversi untuk tujuan non pertanian, maka tanah merah berliat aktivitas rendah merupakan alternatif pengembangan kesinambungan pertanian. Namun tantangannya akan semakin berat karena masalah tersebut. Untuk mengantisipasi pengembangan pertanian pada tanah tersebut, maka penelitian tentang komponen dasar tanah khususnya besi oksida perlu dilakukan. Tujuan penelitian adalah untuk mempelajari karakteristik mineral dan sifat tanah-LAR, serta hubungan besi oksida dengan beberapa sifat fisik dan kimia tanah-LAR.
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Judul: Karakteristik fiska dan mekanika pada berbagai  jenis tanah
Abstrak: Soil physical properties, as well as biologrcal and chemical propwties, affect crop production and growth in relation with water availability and physical environment for plant g~owth. Also, mechanical properties of soil become important in agriculture for learning the soil carrying capacity for agricultural machinery and its effect toward rooting environment. This reseacl~ was conducted with the objective of learning the basic physical, hydraulic and mechanical properties of various types of soil and studying their interrelations with soil colloid. Research method comprise soii sampling in the'fie!d &om various locations in West Java, Central Java and South Sumatra. Analysis of physical, chemical, mineralogical and rnechanicai properties of soil with standard rnethd, was conducted in laboratory of Department of Soil Science, Faculty of Agriculture and Department of Agricultural Engineering Faculty of Agricultural Technology, Bogor Agricultural University fiom January to September 2003 Result of this research show that physical and mechanical properties of each soil type studied, differ from each other. The studied soils have textural classes sandy loam. loamy sand, clay, silty clay and clay loam. Soil with coarse textural class (sandy loam and loamy sand) had buld density ( I . 18 - 1.30 gr/crn3) higher than those of clay textured soit, lower total porosity (5 1.73 - 52.24%), very low Coefficient of Linear Extensibility (COLE) (0.005 - 0.001), Index of aggregate stability (IS A) ranging from very unstable to stable (39.55 - 54.47) and permeability ranging from rapid to very rapid (12.56 - 25.18 d o u r ) . Content of available water in this soil is very low (2.5 - 3.0%) Soil with medium textural class (clay loam) had lower bulk density (0.53 - 0.66 gr/cm3) as compared with bulk density of common m i n d soil, h&er tad porosity (74.30 - 78.58%) as ascompared with clay textured mil (24.5 1 - 68.16%), very high values of COLE (0.268 - 0.353). aggregate stability with ranged from very unstable to stable (32.56 - 4830) an permeability class with was somewhat rapid ( 8.87 - 10.23 cm/hour) . Content of available water in this soil is vw high (32.6 - 35.4%). Soils with clay textural class clay, silty clay and silty clay i loam) had higher bulk density (0.83 - 2.02 gr/cm ) as cumpared with medium textured soils (0.53 - 0.66 gr/cm3). COLE values ranging b m low to very high (0.020 - 0.366), aggregate stab&@ ranging fiom very unstable to very stable (3 1.44 129.551, and permeability ranging h m very slow to modemrely rapid (0.04 - 1 1 -39 cmm0ur)- Available soil water ranged liom very low to very high (3.0 - 26.5%). Most of the mils studied, had kaolinitic clay mineral. Podsolik soil of Jamga and Grumusols had smdte clay miad w h m other types of soil had mixed clay minerd (Planowl of Serang, Alluvial of Kmwang, Muvial of Brebes and Medireran of Ciampea). Soil with medium textural class (Andosd) were dominated by Allophane mineral.
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Judul: Estimating Parameter and the Convergence of Parameter Estimator of Poisson Hidden Markov Model
Abstrak: Model hidden Markov terdiri dari sepasang proses stokastik yaitu proses observasi dan proses yang memengaruhi observasi. Proses stokastik yang memengaruhi observasi ini diasumsikan membentuk rantai Markov dan tidak diamati. Model Poisson hidden Markov (MPHM) adalah salah satu model hidden Markov diskret dan proses observasinya jika diketahui proses yang memengaruhinya diasumsikan menyebar Poisson., A hidden Markov model (HMM) consists of a pair of stochastic processes, that is the observation process and process that affected observation. The stochastic process which causes this observation is assumed to form a Markov chain and is not observed. Poisson hidden Markov models (PHMM) is one of the discrete HMM and the observation process given the cause is assumed having a Poisson distribution.
Keyword: Poisson hidden Markov model, Forward-Backward algorithm, Expectation Maximization algorithm