Journal of Engineering and Technological Sciences
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A Buffer Stock Model to Ensure Price Stabilization and Availability of Seasonal Staple Foods under Free Trade Considerations
Full text linkPrice volatility and scarcity have become a great problem in the distribution system of seasonal staple foods produced by the agricultural industry. There is a salient supply disparity during the harvest and planting seasons. This condition could cause disadvantages to stakeholders such as producers, wholesalers, consumers, and government. This paper proposes a buffer stock model under free-trade considerations to substitute quantitative restrictions and tariffs with an indirect market intervention instrument. This instrument was developed using a buffer stock scheme in accordance with a warehouse receipt system (WRS) and a collateral management system. A public service institution for staple food buffer stock (BLUPP) is proposed as the wholesaler's competitor, with as main responsibility to ensure price stabilization and availability of staple food. Multi-criteria decision-making is formulated as a single objective mixed integer non-linear programming (MINLP) model. The results shows that the proposed model can be applied to solve the distribution problem and can give more promising outcomes than its counterpart, direct market intervention
Linear Parameter-Varying Versus Linear Time-Invariant Reduced-Order Controller Design for Turboprop Aircraft Dynamics
Full text linkThe applicability of parameter-varying reduced-order controllers to aircraft models is proposed. A generalization of the balanced singular perturbation method of the linear time-invariant (LTI) system was used to reduce the order of the linear parameter-varying (LPV) system. Based on the reducedorder model, a low-order LPV controller was designed using the H∞ synthesis technique. The performance of the reduced-order controller was examined by applying it to the lateral-directional control of a 20th-order aircraft model. Furthermore, the time responses of the closed-loop system with several reducedorder LPV controllers and a reduced-order LTI controller were compared. The simulation results show that an , 8th -order LPV controller can maintain stability and provide the same level of closed-loop system performance as a full-order LPV controller. This was not the case with the reduced-order LTI controller, which cannot maintain stability and performance for all allowable parameter trajectories
Confinement of Reinforced-Concrete Columns with NonCode Compliant Confining Reinforcement plus Supplemental Pen-Binder
Full text linkAbstract. One of the important requirements for earthquake resistant building related to confinement is the use of seismic hooks in the hoop or confining reinforcement of reinforced-concrete column elements. However, installation of a confining reinforcement with a 135-degree hook is not easy. Therefore, in practice, many construction workers apply a confining reinforcement with a 90-degree hook (non-code compliant). Based on research and records of recent earthquakes in Indonesia, the use of a non-code compliant confining reinforcement for concrete columns produces structures with poor seismic performance. This paper presents a study that introduces an additional element that is expected to improve the effectiveness of concrete columns confined with a non-code compliant confining reinforcement. The additional element, named a pen-binder, is used to keep the non-code compliant confining reinforcement in place. The effectiveness of this element under pure axial concentric loading was investigatedcomprehensively.The specimens tested in this study were 18 concrete columns,with a cross-section of 170 mm x 170 mm and a height of 480 mm. The main test variables were the material type of the pen-binder, the angle of the hook, and the confining reinforcement configuration.The test results indicate that adding pen -binders can effectively improve the strength and ductility of the column specimens confined with a non-code compliant confining reinforcement.
Structure Refinement of Five Layers Aurivillius Compound: Ba4Bi2Nb2Ti3O18
Full text linkThe room temperature structures of the five layers Aurivillius phase Ba4Bi2Nb2Ti3O18 has been refined from X-ray powder diffraction data using the Rietveld method. The structures consist of [Bi2O2]2+ layers interleaved with perovskite-like [Ba4Nb2Ti3O16]2- blocks. The oxides was found to be orthorhombic (SG B2cb); a = 5.5017(8), b = 5.5031(8), c = 50.363(3) Ã…, Rp = 25.53 Rwp = 35.54 Rexp = 29.30 RBragg = 9.92. The structural features of the compound is found similar to that of other layered Aurivillius compounds. Using the available structural data the ferroelectric properties could be explained and strategies to find good ferroelectric materials could be inferred
Characterization of Chemical and Physical Properties of Hydroxypropylated and Cross-linked Arrowroot (Marantha arundinacea) Starch
No full textThe modern food industry and a variety of food products require tolerant starch as raw material for processing in a broad range of techniques, from preparation to storage and distribution. Dual modification of arrowroot starch using hydroxypropylation and cross-linking was carried out to overcome the lack of native arrowroot starch in food processing application. The modifications applied were: combined propylene oxide (8%, 10%, and 12%); sodium tri meta phosphate/STMP (1%, 2%, and 3%); and sodium tri poly phosphate/STPP (4%, 5%, and 6%). These modifications significantly affected the composition of the amylose and amylopectin and the amount of phosphorus in the granules. Higher amounts of phosphate salt gave a higher phosphorus content, which increased the degree of substitution (DS) and the degree of cross-link. Arrowroot starch that was modified using a concentration of 8-10% propylene oxide and 1-2% STMP : 3-5% STPP produced a starch with < 0.4% phosphorus content. A higher concentration of propylene oxide provided a higher degree of hydroxypropyl. The changed physical properties of the modified granular arrowroot starch were examined through SEM testing, and its changed crystalline patterns through X-ray diffraction measurements. Especially, provision of a high concentration of propylene oxide (12%) combined with 3% STMP : 6% STPP affected the granular morphology and the crystallinity
Determination of Intrinsic Permeability for Packed Waste of Indonesian Solid Waste
Full text linkGas permeability and intrinsic permeability are the major parameters to promote aeration for packed waste. The objectives of this research are to identify physical parameters of gas transfer from a various type of packed wastes and examine ventilation design theory for landfill to enhance waste stabilization. Method to determine value of gas permeability and intrinsic permeability for packed waste is by flushing the packed column containing various type and physical characteristics of wastes with an air pump. Permeability was calculated by measuring pressure gradient on sampling points of the column using inclined manometer at distance 10 cm, 23 cm, 46 cm, 69 cm, 92 cm and 115 cm from origin. Gas permeability is specifically relied on physical parameters of wastes as follows, density, moisture content, particle size and gas velocity on the surface of compacted waste layer. Compost has finer pore structure and smaller pore size than leaves as well as mixed organic (65%) and inorganic wastes (35%). The experiment found the intrinsic permeability of leaves waste are in the order of 10-11 to 10-8 m2, 10-11 to 10-9 m2 for compost and 10-9 m2 for mixed organic (65%) and inorganic wastes (35%)
Laboratory Experiments on Enhanced Oil Recovery with Nitrogen Injection
Full text linkBased on previous studies, nitrogen injection could recover oil up to 45-90% of initial reserves. Although this method has a very good ability to produce oil, sometimes the operation pressure is higher than leak off formation pressure. In this study, operation pressure used a low pressure to solve this problem under immiscible process. Objective of this study is to determine the effect of injection pressure and displacement rate on oil recovery performance of continuous one dimensional nitrogen gas injection with a slim tube apparatus. The effect of nitrogen gas-oil contact on the gas composition was investigated using Gas Chromatograph Mass Spectrometer apparatus. In the experiments, nitrogen gas was injected into an oil sample of 38.5 oAPI gravity at various rates: 20 cc/hr, 30 cc/hr and 36.66/hr under 1500 psi pressure, and then at 20 cc/hr undr 2500 psi pressure. The results showed that an increase in injection rate increased oil recovery factor. The recovery factor lies between 40-54% of original oil in place. Gas analysis before injection and at the injection outlet showed a change of composition. when oil was contacted by nitrogen, indicating that some molecular mass transfer had taken place