The acid failure of aluminium alloy XE aluminium alloy in 2 M hydrochloric acid solution in the presence of Vernonia amygdalina extract was investigated using gasometric technique. Aluminium alloy coupons of dimension 4 cm by 1 cm were immersed in test solutions of free acid and also those containing extract volumes of 2, 3, 4 and 5 cm 3 at ambient temperature for 30 minutes. The volumes of hydrogen gas evolved as a result of the rate of reaction were recorded and analyzed. Analysis revealed that maximum inhibitor efficiency which corresponds to the lowest corrosion rate was obtained at optimum inhibitor volumes of 5 cm 3 , with reduction in the corrosion rate observed to follow in order of increasing extract volumes. Adsorption study revealed that Temkin isotherm best described the metal surface interaction with the extract phytochemicals, with 12 minutes becoming the best exposure time for the phytochemicals to adsorb to the metal surface at all volumes. Statistical modelling of the corrosion rate yielded an important relationship suitable for estimating corrosion rate values once volumes of the extract is known. Microstructural studies, showed an indirect relationship between crack growth rates and extract volumes, while consistency of the irregular intermetallic phases increases with increasing extract volumes.

The price volatility and scarcity have been became a great problem in the distribution system of seasonal staple food produced by agro industry. It has salient supply disparity during the harvest and planting season. This condition could cause disadvantages to the stakeholders such as producer, wholesaler, consumer, and government. This paper proposes a buffer stock model under free trade considerations to substitute quantitative restrictions and tariffs by indirect market intervention instrument. The instrument was developed through buffer stock scheme in accordance with warehouse receipt system (WRS) and collateral management system. The public service institution for staple food buffer stock (BLUPP) is proposed as wholesaler's competitor with main responsibility to ensure price stabilization and availability of staple food. Multi criteria decision making is formulated as single objective a mixed integer non linear programming (MINLP). The result shows that the proposed model can be applied to solve the distribution problem and can give more promising outcome than its counterpart, the direct market intervention instrument.

The use of flare gas as injection gas in miscible gas flooding enhanced oil recovery (MGF-EOR) presents a potential synergy between oil production improvement and greenhouse gases emission mitigation. This work is a preliminary evaluation of the feasibility of miscible flare gas injection based on phase behavior computations of a model oil (43% n -C 5 H 12 : 57% n -C 16 H 34 ) and a model flare gas (91% CH 4 : 9% C 2 H 6 ). The computations employed the multiple mixing-cell model with Peng-Robinson and PC-SAFT equations of state, and compared the minimum miscibility pressure (MMP) value in the cases of flare gas injection and CO 2 injection. For CO 2 injection, both equations of state produced MMP values close to the measured value of 10.55 MPa. Flare gas injection MMP values were predicted to be 3.6-4.5 times those of CO 2 injection. This very high MMP implies high gas compression costs, and may compromise the integrity of the reservoir. Subsequent studies shall explore the gas -oil miscibility behavior of mixtures of flare gas with intermediate hydrocarbon gases and CO 2 , in order to identify a suitable approach for rendering flare gas feasible as an injection gas in MGF-EOR.

In this work we have investigated mixing in a modified orbiting screw mixer (MOSM) designed for solid-solid mixing. Mixing was carried out using urea powder and natural zeolite powder (UZ) of three varying particle sizes (50-60, 60-80 and 80 mesh). Power consumption was calculated from the measured torque of orbit and screw, obtained from computerized records. It was found that the mixing process in the modified orbiting screw mixer with air injection required a lower power consumption for each particle-size group when compared to mixing without air injection. With UZ mixing in MOSM with air injection, the lowest E was obtained for the 60-80 mesh particle-size group (4,297 Joule/kg -1 ), whereas when mixing without air injection, the value was 10,296 J/kg. The best mixing operation in this experiment was achieved at N Fr = 1.18x10 -3 and in the range of values N Re 8.77x10 7 to 2.63x10 8 . Moreover, in this study, we have developed an equation to estimate the power consumption required for mixing and determined its correlation with dimensionless numbers.

Pt-Ni/C alloy nanocatalysts synthesized by polyol method with different atomic ratio are investigated to enhance activity of the oxygen reduction reaction (ORR) for fuel cell applications. Prepared catalysts are characterized by various techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), and cyclic voltammetry (CV). XRD analysis shows that all prepared catalysts with different atomic ratio exhibit face centered cubic and have smaller lattice parameters than pure Pt catalyst. The mean particle size of the catalysts are between 4.3 to 6.3 nm. Cyclic voltammograms with scan rate 5 mV s-1 at 25oC obtain range the electrochemical active surface (EAS) between 40 to 164 cm2/mgPt, mass activity (MA) and specific activity (SA) of nanocatalysts PtNi/C in the potential range 900 mV versus RHE between 3.61 to 8.42 mA/mgPt, and 0.05 to 0.09.

Kaolin has been identified as a potential raw material for the production of -Al2O3 for hydrotreating catalyst support. This work explores the technical feasibility of applying the potassium hydroxide (KOH) e xtraction synthesis route on kaolin from the Belitung Island in Indonesia. The application of a published synthesis method to Belitung kaolin requires an approximately twofold increase in kaolin calcination time, an increase in kaolin calcination temperature from 950 to 1000 °C, and a tenfold increase in metakaolin extraction time, to obtain a specific surface area higher than 200 m2/g. The highest specific surface area of 233 m2/g was obtained when the kaolin was calcined at 1000 °C for 24 hours, and the metakaolin was extracted by concentrated KOH solution for 12 hours. Phase characterization of the final product confirmed the formation of -Al2O3, but with the inclusion of low-surface area -Al2O3 phase.

This paper presents an improvement to dq-domain method of calculating electromagnetic transients. The proposed methodology works on dq-domain model for all components of the power system and during all time iterations. This is a new direction distinct from the old one where the network is invariably modeled in phase-domain. By modeling the network in dq-domain there is no more problem of interfacing machine to network as usually met in the existing method as machine is modeled invariably in dq-domain. Besides eliminating the time consuming transformation procedure between dq-domain to phase-domain or visa versa the new method is able now to fully exploit the infinite stability region of the trapezoidal rule of integration. The prediction/correction procedure of the conventional dq-domain method, which is notoriously known limiting the stability region, is no longer required. Comparing simulations using the new method and ATP, one of the conventional dq-domain version, show perfect conformity for small time step. For long time step while ATP is failing, the new method still converges accurately up to Nyquist’s interval.

This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

Leak detection is always interesting research topic, where leak location and leak rate are two pipeline leaking parameters that should be determined accurately to overcome pipe leaking problems. In this research those two parameters are investigated by developing transmission pipeline model and the leak detection model which is developed using Artificial Neural Network. The mathematical approach needs actual leak data to train the leak detection model, however such data could not be obtained from oil fields. Therefore, for training purposes hypothetical data are developed using the transmission pipeline model, by applying various physical configuration of pipeline and applying oil properties correlations to estimate the value of oil density and viscosity. The various leak locations and leak rates are also represented in this model. The prediction of those two leak parameters will be completed until the total error is less than certain value of tolerance, or until iterations level is reached. To recognize the pattern, forward procedure is conducted. The application of this approach produces conclusion that for certain pipeline network configuration, the higher number of iterations will produce accurate result. The number of iterations depend on the leakage rate, the smaller leakage rate, the higher number of iterations are required. The accuracy of this approach is clearly determined by the quality of training data. Therefore, in the preparation of training data the results of pressure drop calculations should be validated by the real measurement of pressure drop along the pipeline. For the accuracy purposes, there are possibility to change the pressure drop and fluid properties correlations, to get the better results. The results of this research are expected to give real contribution for giving an early detection of oil-spill in oil fields.

Cementing is one of the most important parts in oil-well drilling. Recent development in oil-well drilling technology has led to a more problematic case in cementing. High temperature cementing is one of the problems. High temperature cementing may cover steam recovery wells, geothermal wells and ultra deep wells. The use of expanding cements as an effort to improve the sealing efficacy of annulus cementing has been considered for a long time as a promising solution to the existing problems. CaO and MgO have been proposed as two of the most effective additives to create excellent expanding cement. The purpose of this study is to find the effect of adding up burnt pure CaO and MgO to the value of compressive strength and shear bond strength of API class G cement in high pressure and high temperature condition. The method that we used within this research is an evaluation of the data taken from a simulator that simulated within temperature range of 100 - 250 o C and pressure of 2000 psi. The conclusion is taken according to the results which saying that the addition of burnt pure CaO and MgO would increase the shear bond strength and the compressive strength on specific condition up to 200 o C temperature. The addition won't be effective for the condition of 250 o C temperature. The behavior of cement strength was also influenced by the length of curing time. Further more, research on expanding cement needs to be developed and extended whether to vary its compositions, temperatures, or curing time conditions. The compatibility when mixed with other additives together with silica flour has not yet been figured out.