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This research focuses on determining the level of inventory in a downstream supply chain for fuel products in Indonesian oil and gas company prespective. The variability in supply and demand is a problem in maintaining the stability of services to the consumers. High inventory costs that are completely borne by the company are also a problem that needs to be controlled. Therefore, determining inventory levels is very important to mitigate the variability of supply and demand that occurs with optimum inventory costs. This research designs a probabilistic model by considering variability in supply and demand to determine safety stock so that the correct level of Fuel Product inventory at each Storage Point can be determined. This research method is quantitative research based on empirical data. It is hoped that the research results will be able to obtain inventory control which can be taken into consideration by oil and gas company in managing the downstream supply chain of fuel products. [ABSTRACT FROM AUTHOR]

Filament winding is a widely used method for producing tubes and pressure vessels from composite materials. However, overlapping of fibers during the winding process can lead to rough surface and increased voids in the finished product. To improve the quality of CFRP materials produced through filament winding, the structure is cured either at room temperature or in an oven with a controlled heat profile, depending on the type of resin used. Various finishing techniques, including shrink tape, compression molding, and vacuum compression molding, have been attempted to improve the quality of the specimen. Among these techniques, vacuum compression molding has been found to deliver the best results in terms of surface roughness, with average roughness (Ra) values of 0.35 μm in the fiber direction and 0.61 μm in the transverse direction. This level of roughness is comparable to that achieved through milling machine manufacturing. Moreover, this technique ensures uniformity in fiber composition and volume fraction, achieving a homogeneous density of 1364.49 kg/m³ and the highest fiber volume fraction of 63 %. As a result, remarkable mechanical attributes, such as a tensile strength of 926.07 MPa and a stiffness of 21.35 GPa, can be obtained. In addition, by utilizing various finishing techniques, the tensile strength of these properties can be increased by up to 80 %. CFRP is a versatile material with unique characteristics, and selecting appropriate finishing techniques such as vacuum compression molding can significantly enhance its overall quality and mechanical properties. However, one drawback of the filament winding method is the poor outer surface finish which can be improved by vacuum compression molding. [ABSTRACT FROM AUTHOR]

The fabrication of a natural prepreg with poly-lactic acid (PLA) matrix and ramie fiber reinforcement was engineered on a laboratory scale by impregnating the unidirectional and bidirectional ramie fiber with PLA matrix solvent on a glass die. The obtained composite prepreg has been stored at a very low temperature to maximize its shelf life. Tensile and biodegradability tests of the composite laminates prepared by the hot-pressing method have also been conducted. Tensile test results show that the freezer-stored bidirectional 0/90° prepreg laminate specimen has the highest tensile strength of 71.44 MPa with a modulus of 2.70 GPa on average. Meanwhile, the unstored bidirectional 0/90° prepreg laminate specimen has the highest level of elasticity, with a modulus of 1.29 GPa on average. The biodegradability test shows the decomposition process of the composite laminate under actual composting conditions. Microscopic observation of the damaged specimen results shows good adhesion between the PLA matrix and ramie fiber and the decomposition of the biodegradability test samples. [ABSTRACT FROM AUTHOR]

As the research on composite materials based on natural resources proliferates further, ramie fiber and polylactic acid (PLA), whch are fully biodegradable composite materials, are expected to be used for mechanical application due to their excellent strength and degradability. Various natural fibers have been applied to a wind turbine blade composite structure, as reinforcement material. However, none of them are fully biodegradable, as the matrix still uses synthetic resins. Hence, this study aims to theoretically optimize the fully biodegradable ramie/PLA laminate design using its lamina orientation on a taper-less blade shell of a wind turbine, as the operating structure experienced multiaxial loading through bending and torsional moment derived by the wind. The selection of taper-less blades was made due to their congruence with the wind speed categorization in southeastern Indonesian territory. The optimization was carried out using the nonlinear Generalized Reduced Gradient (GRG) method on Microsoft Excel. The optimized laminate result is in a stacking sequence of [-4°, 24°, 47°, 65°, 74°, 79°]S that delivers the factor of safety, which is the ratio between the allowable stress and the actual stress, of 7.296 and 18.057 on the longitudinal axis and the laminate shear-plane, respectively, This renders the composite laminate highly safe, both theoretically and numerically. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effect of using acrylonitrile butadiene styrene in place of conventional wax material on treatment pattern removal in the investment casting process. There are three controllable process variables that can affect treatment pattern removal, which include temperature increase, holding time and the number of layers of ceramic shell that have been considered for comparison. Comparison among the effects of temperature increase, holding time and numbers of ceramic shell layers on the ceramic shell was analyzed using ANOVA. It was found that temperature increase (Tx), holding time (t) and number of layers of ceramic shell (N) contribute significantly to the length of the crack (l) on the ceramic shell. The crack in the ceramic shell's surface was analyzed using scanning electron microscope photos. Less layers number cause the increase of crack length. The combination between temperature upraise and longer holding time cause cracking delay. The experimental is conducted by using 3 (three) variants for each of layers number, temperature and holding time. The layers number is ranging between 7-9 layers. Temperature increase from room temperature until 1300oC. The layers number variant is ranging between 180-300 seconds. It was concluded that a longer holding time will result in a more intact ceramic shell, as longer holding times yield short crack lengths. [ABSTRACT FROM AUTHOR]