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1.
《Chemometrics and Intelligent Laboratory Systems》1999,45(1-2):39-53
A contrast method originally proposed by Spiegelman [C.H. Spiegelman, Calibration: a look at the mix of theory, methods and experimental data, presented at Compana '95, Wuerzburg, Germany.] is modified to pretreat multivariate data for classification. Three NIR data sets and one pollution data set are used as examples. Our results show that the contrast method greatly improves the ratios of between- to within-class variance. It is more powerful than offset correction, SNV, first- and second-derivative methods in the cases studied. This conclusion does not depend on the type of classifier used. Regularised discriminant analysis (RDA) and partial least squares (PLS2) with univariate feature selection based on Fisher's ratio were applied here. There is a risk that chance correlations occur after the contrast pretreatment. The chance correlation decreases after first eliminating un-informative variables using the modified Uninformative Variable Elimination (UVE)-PLS method. 相似文献
2.
J. Zare 《Petroleum Science and Technology》2013,31(15):1833-1842
One of the advantages of managed pressure drilling (MPD) is an increase in drilling speed and a reduction of mud filtrate invasion as a result of decreasing pressure differential. Reduction of overbalanced pressure (OBP) leads to a decrease of confining pressure around the formation rock and consequently the rock is broken more easily under the bit action and therefore the rate of penetration (ROP) increases. It is also obvious that decreasing the overbalanced pressure results a reduction in mud filtrate invasion and formation damage. In the present article the effect of MPD on increasing rate of penetration and decreasing mud filtrate invasion is studied. Artificial neural networks (ANN) were implemented to develop a model for estimation of ROP by using operational inputs including overbalanced pressure. Using the ANN model, the effect of OBP was analyzed. The effect of OBP on mud filtrate invasion was studied by using developed models of the process and simple Darcy’s law. The results demonstrated that MPD leads to about 30% increase in rate of penetration and 50% decrease in mud filtrate invasion. 相似文献
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4.
Methane/natural gas storage and delivered capacity for activated carbons in dry and wet conditions 总被引:1,自引:0,他引:1
Methane/natural gas storage and delivered capacity for three different activated carbons in dry and wet conditions were measured. In all tests the temperature of the bed was maintained constant at 277.15 K and pressure was increased up to 10 MPa. Natural gas storage capacity was less than methane storage capacity in dry conditions for all the three activated carbons tested, while the gas delivery was almost the same. One of activated carbon tested (NC120) showed the possibility of hydrate forming for pressures higher than 4 MPa but the amount of gas stored still was less than the amount stored in dry conditions over the whole range of pressure. The analysis of the gas delivered at each pressure steps shows that considerable amount of heavy components do not come out from the bed even at very low pressures in both dry and wet condition tests. Repeatability of the sorption/desorption processes - vital for possible commercial/industrial use - has been examined over various cycles. 相似文献
5.
Ali Abedini Siavash Ashoori Farshid Torabi Yaser Saki Navid Dinarvand 《Journal of Petroleum Science and Engineering》2011,78(2):316-320
Asphaltene precipitation and deposition occur in petroleum reservoirs as a change in pressure, temperature and liquid phase composition and reduce the oil recovery considerably. In addition to these, asphaltene precipitates may deposit in the pore spaces of reservoir rock and form plugging, which is referred to as a type of formation damage, i.e. permeability reduction. In all cases above, it is of great importance to know under which conditions the asphaltenes precipitate and to what extent precipitated asphaltenes can be re-dissolved. In other words, to what extent the process of asphaltene precipitation is reversible with respect to change in thermodynamic conditions. In present work, a series of experiments was designed and carried out to quantitatively distinguish the reversibility of asphaltene precipitation upon the change in pressure, temperature and liquid composition. Experiments were conducted in non-porous media. Generally it was observed that the asphaltene precipitation is a partial reversible process for oil under study upon temperature change with hysteresis. However, the precipitation of asphaltene as a function of mixture composition and pressure is nearly reversible with a little hysteresis. 相似文献
6.
Ethylene oxide production process is one of the highest energy consumers in chemical industry, and therefore even a slight improvement in its overall efficiency can have a significant impact on the sustainability of the process. Efficiency improvement can be carried out using the exergy-aided pinch analysis outlined in this paper. The overall exergy loss distribution in different unit operations of an ethylene oxide process was first evaluated and mapped out in the form of “visualized exergetic process flowsheet”. An initial analysis of the four main functional blocks of the process showed that the exothermic reaction block contained the largest exergy loss (6043 and 428 kJ/kg of internal and external losses, respectively) which can be reduced by isothermal mixing, as well as increasing reaction temperature and reduction in pressure drop. The absorption block was also estimated to have the second highest contribution with total exergy losses of 3640 kJ/kg which were mainly due to the cooling column. These losses were then recommended to be reduced by improvements in the concentration and temperature gradients along the tower. Following the block-wise analysis, exergy analysis was then carried out for individual unit operations in each block to pinpoint the main sources of thermal exergetic inefficiency. Thermal solutions to reduce losses were also proposed in accordance with the identified sources of inefficiency, leading to a comprehensive list of cold and hot process streams that could be introduced to reduce losses. Finally, pinch analysis was brought into action to estimate the minimum energy requirements, to select utilities, and to design heat exchanger network. Thus, the methodology used in this work took advantage of both exergy and pinch analyses. The combined thermal-exergy-based pinch approach helped to set energy targets so that all the thermal possible solutions supported by exergy analysis were considered, preventing exclusion of any hot or cold process stream with high potential for heat integration during pinch analysis. Results indicated that the minimum cold utility requirement could be reduced from 601.64 MW (obtained via conventional pinch analysis) to 577.82 MW through screening of streams by the combined methodology. 相似文献
7.
Karim Salahshoor Ehsan Safari Iraj Ahangari 《Engineering Applications of Artificial Intelligence》2013,26(5-6):1512-1531
This paper proposes a new adaptive nonlinear model predictive control (NMPC) methodology for a class of hybrid systems with mixed inputs. For this purpose, an online fuzzy identification approach is presented to recursively estimate an evolving Takagi–Sugeno (eTS) model for the hybrid systems based on a potential clustering scheme. A receding horizon adaptive NMPC is then devised on the basis of the online identified eTS fuzzy model. The nonlinear MPC optimization problem is solved by a genetic algorithm (GA). Diverse sets of test scenarios have been conducted to comparatively demonstrate the robust performance of the proposed adaptive NMPC methodology on the challenging start-up operation of a hybrid continuous stirred tank reactor (CSTR) benchmark problem. 相似文献
8.
《International Journal of Heat and Mass Transfer》2006,49(1-2):329-340
Entrained fluid heat capacity is shown to have a significant and positive effect on the performance of a passive regenerator. The ineffectiveness of the regenerator is presented as a function of three dimensionless parameters: the number of transfer units, the utilization, and the entrained fluid to matrix heat capacity ratio. Three different behaviors are observed for a regenerator with entrained fluid heat capacity. The effect of the entrained fluid can be accounted for over a large range of conditions using the concept of an augmented-NTU which can be substituted for the actual NTU in analyses that neglect entrained fluid capacity. 相似文献
9.
Well productivity is a crucial concern in predicting the performance of many gas condensate reservoirs. Accurate forecasting of gas-condensate well productivity usually requires fine-grid simulation to model the formation of the liquid bank and to account for high-velocity phenomena and changes in relative permeability at high capillary numbers. At early stages of production, the pressure drop in the near-wellbore region builds up the molar content of water in gas. This, in turn, results in water vaporization, and hence a drop in the connate water saturation. When water vaporization occurs, pores that were formerly filled by connate water now becomes occupied by gas and condensate only. This causes a change in gas and condensate saturations near the wellbore that can affect the well productivity. No lucid numerical simulation approach considering this effect is suggested in the literature. The authors investigated the effects of water vaporization on the near-wellbore region by compositional simulator of GEM. Enhancement of gas well productivity is observed. 相似文献
10.
Mohammad Mohammadian Maryam Ahmadi Mohammad Reza Khosravi-Nikou 《Petroleum Science and Technology》2017,35(6):608-614
Adsorption of heterocyclic sulfur- and nitrogen-containing compounds by mesostructure adsorbent (MSU-S) and its modified form with cobalt oxide is studied using model fuel. The results of characteristic tests (XRD, N2 adsorption–desorption, FTIR, and SEM) indicate that CoO impregnation causes a negative impact on mesoporous structure, crystalline phase, and particle shape along with a positive effect on surface ion exchange. CoO modification increased the adsorption loadings of DBT and BT to about 33.6% and 45.7%, respectively. For nitrogen compounds adsorption with the model fuel, adsorption loadings of quinoline and carbazole increase by 6.7% and 8.6%, respectively. Data fitting for carbazole, DBT, and BT is achieved better by the Langmuir model than the Freundlich model, and the data of quinoline fitted very well to the Freundlich model for CoO-MSU-S. 相似文献