Judul: Estimasi Emisi Metana pada Lingkungan Rumen in Vitro menggunakan Artificial Neural Network
Abstrak: The production of methane from ruminants contributes significantly for the total methane emissions in the atmosphere. Methane is one of the greenhouse gases that causes global warming. Its ability to retain heat is of 20 times bigger than that of carbon dioxide. In this research, Artificial Neural Networks (ANNs) are used to estimate the methane emissions from volatile fatty acid (vfa) composition in the rumen in vitro; acetate (C2), propionate (C3), butyrate (C4), iso-C4, (valerate) C5, and iso-C5. In this research, after careful tuning, we obtained the best ANNs with the NMSE of 0.0182. This suggests that ANN outperform the stoichiometric equation in ability to estimate methane emissions in the rumen
Keyword: Bogor Agricultural University (IPB), stoichiometric, ruminant, methane, forage, Artificial Neural Network

Judul: Estimasi Emisi Gas Metan yang Dihasilkan dari Fermentasi Hijauan Tropis dalam Rumen In Vitro Melalui Komposisi Asam Lemak Terbang
Abstrak: Rumen is the home to billions of microbes, including bacteria, methanogens, protozoa and fungi. These microbes breakdown feed to produce volatile fatty acids (VFA), carbon dioxide, ammonia and methane (CH4). Metabolic hydrogen in the form of reduced protons (H) is used during CH4 formation as well as during VFA synthesis. Therefore, VFA molar proportion in the rumen is stoichiometrically related to CH4 emission. The aim of this study was to evaluate methane emission between experimental and model estimates. The data sets were obtained from a published literature. Samples used were leaves from 27 tropical plant species. Model comparison was based on Duncan’s test. Prediction error was conducted by computing mean square prediction error (MSPE) and root mean square prediction error (RMSPE). Results showed that linear equation of Moss model to CH4 observed before adjustment was y = 0.4231x – 3.1762 with R2 = 0.4645, whereas Hegarty model to CH4 observed before adjusment was y = 0.3735x – 3.2963 with R2 = 0.4778. Further, linear equation of Moss model to CH4 observed after adjusment was y = 0.8446x – 4.6719 with R2 = 0.6619, while Hegarty model to CH4 observed after adjustment was y = 0.7405x – 4.8011 with R2 = 0.6714. Validation assessment showed that estimation model of Moss et al. (2000) had lower RMSPE value, i.e. 8.01%, than that of Hegarty and Nolan (2007) model, i.e. 10.73%. This study demonstrated that the low or high methane emission can be estimated by VFA composition with a sufficient accuracy. Adjusment by considering H2 recovery lowered the bias significantly. Comparison of predicted versus observed CH4 production showed that Moss model had closer to the ideal line (where predicted values are the same with the observed values) than Hegarty model.
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Judul: Karakteristik lompatan hidrolik terhadap pelimpah terjunan pada saluran segi empat
Abstrak: Aliran dengan kecepatan tinggi dalam kondisi superkritis yang melintasi bangunan pelimpah, sebelum bergerak lebih jauh ke arah hilir saluran dimana bilangan Froude (F) lebih besar dari satu harus diubah menjadi aliran subkritis dimana bilangan Froudenya lebih kecil dari satu. Aliran yang meninggalkan kaki pelimpah merupakan aliran yang memiliki kandungan energi yang amat berarti sehingga dapat menimbulkan pengikisan yang besar. Pengubahan bilangan Froude dari kondisi superkritis ke subkritis dimaksudkan agar terjadi perubahan kandungan energi, sehingga aliran menjadi non erosive. Agar daya erosive aliran dapat berkurang, maka biasanya pada bagian hilir dari bangunan pelimpah dibuatkan suatu bangunan peredam energi. Erosi yang terjadi di hilir bangunan pelimpah dapat disebabkan dari keberadaan bangunan pelimpah itu sendiri, maupun bangunan peredam energi yang kurang tepat. Hal ini terutama menyangkut beberapa kejadian lompatan hidrolik yang timbul pada bangunan peredam energi tersebut.. Suatu metode yang efektif untuk menjamin bahwa lompatan hidrolik selalu terjadi pada daerah yang dilindungi, adalah dengan menggunakan bangunan peredam energi yang terdiri dari beberapa tipe dengan..dst
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