ITK

Abstract: Penggunaan komposit berbahan dasar fiberglass banyak dijumpai dalam pembuatan kapal. Akan tetapi, penggunaan komposit pada proses pembuatan kapal belum memiliki standar mutu yang jelas dan baku mengenai perbandingan antara jumlah resin dan katalis yang digunakan. Sedangkan, jumlah penggunaan resin dan katalis memiliki pengaruh terhadap kekuatan dari komposit berpenguat serat. Penelitian ini bertujuan untuk mengetahui pengaruh jumlah katalis yang dicampurkan ke resin terhadap kekuatan tarik komposit fiberglass-polyester . Metode yang digunakan dalam penelitian ini adalah metode eksperimen yang menggunakan mesin pengujian tarik dengan memvariasikan jumlah katalis pada resin dari 0,5% sampai dengan 2%. Pada penelitian ini diperoleh hasil bahwa komposit dengan jumlah katalis 0,5% memiliki nilai kekuatan tarik 4,85 kgf/mm 2 , elongasi 2,43% dan modulus elastisitas 2,26 kgf/mm 2 . Komposit dengan jumlah katalis 1% memiliki nilai kekuatan tarik 5,02 kgf/mm 2 , elongasi 1,71% dan modulus elastisitas 2,96 kgf/mm 2 . Komposit dengan jumlah katalis 1,5% memiliki nilai kekuatan tarik 5,49 kgf/mm 2 , elongasi 1,97% dan modulus elastisitas 3,07 kgf/mm 2 . Komposit dengan jumlah katalis 2% memiliki nilai kekuatan tarik 4,97 kgf/mm 2 , elongasi 1,62% dan modulus elastisitas 3,11 kgf/mm 2 . Kekuatan tarik komposit fiberglass-polyester mengalami peningkatan di jumlah katalis 0,5 hingga 1,5% dan mengalami penurunan di jumlah katalis 2%. Nilai kekuatan tarik tertinggi terdapat pada komposit dengan komposisi jumlah resin 100% dan jumlah katalis 1,5%.-

Abstract: Decision making in vine protection against powdery mildew is complex since this disease must be treated before symptoms appear. To trigger treatments only when needed, decision support systems should combine precise models with decision rules. The latter may have to be adapted according to climate and national policies. Therefore, model simulated variables must be rich enough to feed different rules. This work describes a methodology to design such a model from heterogeneous scientific literature. It also reviews to what extent observation of severity databases enables evaluation of the quality of model and decision rules.

Abstract: This work describes the global sensitivity analysis (SA) of an agro-climatic model embedded in a decision support system (DSS) for the water status management of vineyard in the Languedoc-Roussillon region, France.

Abstract: In oil palm plantations, addition of nitrogen (N) via legume cover crops and fertilisers is a common practice to achieve the yield potential of the crop. It is associated with effects on climate change through emissions of N2O (Choo et al., 2011). As oil palm is the most rapidly expanding tropical perennial crop, and is expected to keep expanding in the next decades (Corley, 2009), this raises environmental concerns. We reviewed the available measurements for N2O and other N fluxes in oil palm plantations on mineral soils (Pardon et al., 2016). We saw that direct N2O emissions were the most uncertain N flux, ranging from 0.01 to 7.3 kg N ha-1 yr-1, with a tendency to be higher during the immature phase, to decrease with the age of palms and to be higher in poorly drained soils (Ishizuka et al., 2005; Banabas, 2007). However, only very few measurements were available on mineral soils, and data is still lacking to better understand the potential effects of spatial heterogeneity in plantations (soil properties, soil cover) and management practices (e.g. fertiliser application timing, splitting, placement). Indirect N2O emissions were related to emissions of NH3 and NO3- which were particularly high during the immature phase when the N inputs are high while the palms are still young. We compared 11 existing models and 25 sub-models to simulate oil palm N budget and losses, among which 8, 9 and 8 sub-models were specific to N2O emissions, NH3 volatilisation, and NO3- losses through leaching and runoff; respectively (Pardon et al., under review). We saw that direct N2O emissions estimates were some of the most variable across models, ranging from 0.3 to 7 kg N ha-1 yr-1 (Mosier et al., 1998; Bouwman et al., 2002b; IPCC 2006, from Eggleston et al., 2006; Crutzen et al., 2008; Meier et al., 2012; APSIM from Huth et al., 2014 ; Shcherbak et al., 2014). The main influential factors on direct N2O emissions were the rate of mineral fertiliser applied and the emission factors of the models. The models accounting for felled palms decomposition, empty fruit bunches applications, and biological N fixation also estimated a peak of N2O emissions during the immature phase. Therefore direct and indirect emissions of N2O in oil palm plantations seemed not to be negligible in terms of environmental effect, with ranges of 11 to 2,425 and 79 to 2,443 kg CO2e ha-1 yr-1 for measured and modelled values; respectively (assuming a global warming potential of 298 for N2O). However, in order to be able to adapt management practices to mitigate these emissions, knowledge is still lacking to better understand the potential effects of spatial heterogeneity and management practices on direct and indirect N2O emissions The main modelling challenges are to model the impact of management practices, taking into account the soil N dynamics and residues decomposition, and this over the whole cycle.