Escalation fuel consumption occurs in various regions of the world. However, world oil reserves decline from year to year so that it becomes scarce and causes oil prices to surge up. This problem can be solved by saving fuel consumption. One method of saving fuel is adding bio-additives from citronella oil as a sustainable resource to diesel fuels. Citronellal, citronellol and geraniol are the main components of citronella oil which can be used as fuel additives. This study aimed to evaluate the effect of citronella oil fractions as bio-additives to the performance of diesel engine. The research stages include: extraction of citronella oil, vacuum fractionation of citronella oil, physical chemical characterization of citronella oil and its fractions, formulation of bio-additive -fuel blending, characterization of blending, and evaluation of fuel efficiency. The effect of concentration of the bio-additives was examined towards three diesel fuels; dexlite, pertamina-dex, and biosolar. The results showed two main fractions of citronella oil; citronellal dominant component (FA) and citronellol-geraniol dominant components (FB). The concentration variation of bio-additives was 0.1–0.5%. Fuel consumption efficiency was tested using diesel engine at an engine speed of 2000 rpm and a load increment of 1000, 2000 and 3000 psi with 7 min running time. The fractions represented the different tendencies to enhance the fuel efficiency up to 46%, influenced by the mixture’s concentration. Generally, citronella oil and the fractions showed the potency as bio-additive to diesel fuels.

Recently, 3D printing technology has become a practical method to realize products rapidly. It is suitable for making small quantities of products. Although it is capable of printing with a high level of geometric complexity, there is a lack of tensile strength due to its process where the products are printed layer by layer. However, this technology is potentially to be combined in a composite manufacturing process. Mostly, a composite product is made by using a mold. This mold is relatively expensive and can only create a product with less complexity. Nevertheless, the composite product has main advantages such as light, strong, and flexible. Therefore, combining these two technologies is a new breakthrough in realizing products with high complexity, light, strong, and flexible. This study aims to determine the mechanical properties of sandwich composite filled with 3D printed product as a core. Several parameters were varied including core thickness and skin thickness. The skin material was a Glass Fiber Reinforced Polymer (GFRP) while the core material was 3D printed Polylactic Acid (PLA). The tensile and bending tests have been done in accordance with ASTM D638 and ASTM D790. The results showed that the addition of GFRP skin on the sandwich composite could significantly increase the tensile strength but did not have an impact on the flexural strength. The highest flexural strength of 50.36 MPa was achieved at 3 layers of GFRP skin while a remarkable tensile strength of 55.74 MPa was obtained at 4 layers GFRP skin. Moreover, the addition of core thickness also does not have an impact on flexural strength. The flexural strength of the 3D printed core was around 20 MPa for all thickness. However, when 2 layers of GFRP skin were used, a remarkable flexural strength of 57.67 MPa was obtained but the flexural strength was then decreased when using 10 and 15 mm cores.

Study has showed that Greenhouse gases are the main contribution to global warming. Climate modeling is one of method to explain the influence of those gasses to global warming. Many climate modeling have been proposed to analyze global warming process. Among them, Zero-Dimensional model as the simple model is able to generally describe the influence factors of the climate process. It is important to know the characteristic of each parameter by re-examining the current model. The model derived by Boeker-Van Grondelle offers simple description of global climate processes occurred. The model is system equations consists of two equations and variables. The systems are being studied by using two numerical methods, namely: Multiple-Equation Newton-Raphson and Steepest Descent Method. The accuracy of both methods was analyzed to obtain the best solution to the system equations. The proposed solution was verifying by the result that previously published. Index Terms-Climate modeling, numerical methods, Newton-Raphson and Steepest Descent.

Abstract. NACA0012H is an airfoil type that could be used for Unmanned Aerial Vehicle Medium Altitude Long Endurance. This experiment was used to analyze stress in the surface of Tail of UAV MALE that was caused by air flow. The experiment was conducted using Computational Fluid Dynamics Software. Two designs of tail, horizontal and V-tail, were considered to simulate pressure occurred on the surface of leading edge, chamber and trailing edge. The simulation was developed varying the speed of the UAV MALE. The results showed that pressure occurred on the surface of horizontal tail higher than pressure on the V-tail.

No abstract