توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱A fracture mechanics approach for analyzing spiral weld pipes containing crack
نویسنده(ها): ،
اطلاعات انتشار: اولین کنفرانس لوله و صنایع وابسته، سال
تعداد صفحات: ۹
Spiral weld pipes are used extensively in the gas and oil industries. Compared to the longitudinal seam pipes, the spiral weld pipes can be manufactured straighter, rounder, longer and with more uniform stress distribution and higher rigidity. However, because of the longer weld line these pipes are more susceptible to damage due to the growth of cracks and defects which exist or are generated in the weldment area. Therefore, it is important to investigate the integrity and the remaining service life for the defected spiral weld pipes. Due to the arbitrary orientation of cracks and application of various external loads in spiral pipes, these pipes experience complex state of stress and deformation. In such cases, crack growth may occur under any combination of shear and tensile loads in the cracked area. In this paper, the application of a fracture criterion called the maximum hoop stress (MHS) criterion is described for predicting the integrity of cracked spiral weld pipes. This criterion can evaluate both the direction of fracture initiation and the final sustainable load of gas and oil pipes containing crack. The failure design curve which is presented in this paper for different loading types and crack orientations can be used for failure assessment of cracked spiral weld pipes or other similar engineering applications.<\div>

۲Numerical Calculation of Saturation profile in Stratified Porous Media during GOGD process
نویسنده(ها): ، ، ،
اطلاعات انتشار: دهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۱۳
Numerical technique has been used to find the liquid saturation profile in layered porous media under the gravity drainage process. Geological surveys clearly indicate that all the sedimentary rocks beneath of the earth are made of different layers. Each layer has its own characteristics
such as porosity, permeability, capillary pressure and even wettability. The oil saturation profile during the gas oil gravity drainage (GOGD) process plays an important role for oil recovery efficiency. The oil trapping in the dense layer on the top of more permeable layer is responsible
for the low oil recovery during the primary, secondary and even tertiary oil recovery governed by gravity forces. This numerical scheme reveals the importance of capillary pressure in the vicinity of two different layers for the calculation of saturation profile. Several different tests including the single high permeable layer, single low permeable layer, low over the high and high on low permeable strata are done using the proposed technique which are qualitatively confirmed by using two dimensional sintered glass bead models.<\div>

۳Temperature effects on Gas–Oil Gravity Drainage in sand packed models
نویسنده(ها): ، ،
اطلاعات انتشار: دهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۱۱
It is known that the oil content in matrix porosity in some of the fractured oil reservoirs exceeds more than 90% of the oil originally in place. Minimal recovery factors during the primary stages of production are due to the nature of these reservoirs; geometry and extent of the fracture
network, matrix permeability, wettability tendency, as well as the nature of the fluid system. The occurrence of a strong water drive, in some of the fields, becomes even more detrimental to primary recovery. Besides, having very active water drives, some of these reservoirs are already
depleted resulting in very high residual oil in place. The oil recovery factor in these reservoirs was also hindered due to heavy oil viscosity as well as very high water cut production during the traditional oil recovery mechanisms. Gas–Oil Gravity Drainage (GOGD) has been found as a very efficient process of secondary and tertiary oil recovery. Temperature effects on the improvement of GOGD process for the recovery of heavy oil has been investigated here. High oil recovery factor was achieved during the multiple processes of free fall gravity drainage, pressure aintenance and thermal simulation from the fractured and non–fractured water–wet sand packed models. It was also noted that a combination of waterflooding and GOGD process is very effective to enhance heavy oil recovery from fractured water–wet porous media.<\div>

۴Fracture Resistance of a Synthetic Rock Subjected to Combined Mode I–II Loading
نویسنده(ها): ،
اطلاعات انتشار: سومین کنفرانس مکانیک سنگ ایران، سال
تعداد صفحات: ۸
Crack growth in rock materials generally occurs due to a combined effect of shear and tensile loads. Therefore, assessment of rock fracture esistance under combined mode I–II is inevitable. Although there are numerous experimental data in the literature for combined mode I–II fracture toughness of rocks, the available fracture theories are not able to predict the fracture toughness values obtained from some of the experimental results. In this research, a modified fracture theory is used for predicting the combined mode I–II fracture toughness of brittle materials like rocks. It is shown that the modified theory can provide much better predictions for the experimental data reported from fracture tests conducted on a synthetic soft rock.<\div>

۵A New Method for Musical Noise Detection and Evaluation in the Noise Reduction SYstems
نویسنده(ها): ، ، ،
اطلاعات انتشار: سال
تعداد صفحات: ۶
Subjective listening tests lead lo the ntost reliable results in evaluating the speech quality; hov,ever, they are very costly and time consuming–
Thus an objective measure which can predict the perceived subjective quality speech would be very helpful In this paper a new method for detecting the wide–band musical noise in the acoustic signal is proposed. Musical noise is one of the major distortiorts introduced into the background noise when processed by a noise reduction system. In this paper also an objective measure is proposed which can determine the
amount of the musicalness of the residual noise. The performance of the proposed measure was verified using subjectite listening tests. istening tests shov the high correlation of lhe proposed measure u'ilh lhe perceived subjective quality ofthe background noise<\div>

۶A New Stochastic Integral Pulse Frequency Modulator Based Model for HRV Generation
نویسنده(ها): ، ، ،
اطلاعات انتشار: پانزدهیمن کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۴
The time intewals berween two sttccessive Rwaves (the largest amplitude of the normal ECG) give the RR tachogram, which contains very important information about the dynamic response of the cardiovascular control system to changes of physiological conditions. Devising a mathematical model to produce this RR tachogram time series (i.e. an artificial ECG signal generator) has attracted consi der a b I e int er ests r ec ently. In a previotts work flJ, we developed a new nonlinear model for an ECG generator, which sttccessftilly produced the RRtachogram and the actions ofthe intercoupling between sympathetic and parasympathetic systems. In this present study, we upgrade our previous model by considering a new stochastic process in order to improve its performance in generating the heart rate variability (HRV). The modified model is able to produce RR–interval time series with power spectrum hrming very low frequency and Mayer waves components, as well as the respiration sinus arrlrythmia (RSA) component. In addition, stochastic behqvior in the simulated HRV signal was also observed, which is similar to that observed in real clinical recordings.<\div>

۷Effects of Preloading Level on a Warm Pre– Stressed Crack Speciman
نویسنده(ها): ،
اطلاعات انتشار: سیزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۷
The residual stress and the crack tip blunting are two major suggested mechanisms for justifying the improvement in the load bearing capacity of cracked specimens after warm pre–stressing. In this paper, the finite element method is used to simulate the warm pre–stressing in a three–point bend specimen. The specimen is preloaded and its effect on these two mechanisms is investigated. It is shown that in general both the residual stress and the crack tip blunting are important in warm pre–stre ssing. However, depending on the level of applied preload one of them can be considered as the main cause. It is shown that in low levels of preloading crack tip blunting is more influential and in contrast, it is compressive residual stress that plays more important role in high levels of preloading.<\div>

۸Energy Transfer in Tertiary Oil Recovery by Steam Injection
نویسنده(ها): ، ،
اطلاعات انتشار: یازدهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۱۱
The purpose of this investigation was to study energy and mass transfer in thermal oil recovery in porous media. A set of multistage laboratory tests was performed to find the effects of temperature on the viscosity of waterflood residual heavy oil during steam injection. Sand packed models were utilized to investigate the porosity, permeability, and sand size distribution on the recovery of waterflood residual oil. An oil bank was formed in steam injection during the tertiary oil recovery which results very high oil recovery efficiency. Steam injection was found to be very effective, compared to coldand hot–water flooding, for the recovery of heavy oil. A mathematical model was developed to predict the temperature profile during the steam injection process. Satisfactory agreement is achieved between the temperature profile, predicted from the model, and the experimental results<\div>

۹Simulation of Dissociation Extractive Crystallization Process in Ionic Media
نویسنده(ها): ،
اطلاعات انتشار: یازدهمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۱۱
Dissociation extractive crystallization (DEC) is a novel separation process that shows its efficacy in the separation of close boiling and isomeric components, where the conventional methods are not effective. The intention of this study is to develop a theoretical basis for solution phase behaviour and to provide a simulation model for the process in ionic media. The model utilizes the UNIFAC method and it can predict the concentrations of all species after adding reagent as well as the fractional recovery of the process. The validity of the model has been assessed by the experimental results achieved in the separation of dichloroacetic acid (DCA) and trichloroacetic acid (TCA) in aqueous media. To enable the model for such a task, the UNIFAC has been modified to be able to predict the activity coefficient of neutral molecules in the presence of the ionic particles. The experimental and predicted results present on ternary solid–liquid phase equilibrium diagrams for the DCA – TCA – water system. A good agreement is found between the predicted results from the separation model and the experimental ones for such a complex system.<\div>

۱۰Conditional Non–Central Moments and Characteristic Function Based on Matching Pursuit
نویسنده(ها): ،
اطلاعات انتشار: سیزدهیمن کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۵
In this paper, we decompose a non–stationary signal by use of the matching pursuit (MP) algorithm, through using two different types of dictionaries (i.e., the Gaussian and chirplet dictionaries). Then we give expressions for the first and second–order conditional spectral moments, which are generalizations of the ideas of instantaneous frequency and instantaneous bandwidth. Although in many cases the second–order conditional spectral moment is not positive and this makes the usual interpretation of this quantity impossible, with MP decomposition, by using the Gaussian or chirplet dictionaries, the second–order conditional spectral moment is always positive. In addition, we derive the characteristic function for the MP distribution. So the joint higher–order statistical moments can be calculated by differentiation simply. We also analyze a bat sound signal with short time Fourier transform (STFT) as well as the adaptive signal decomposition, MP, and compare the resolution of relative time–frequency distributions.<\div>

۱۱A Comprehensive Model for Generating ECG Signals Using IPFM Model
نویسنده(ها): ، ،
اطلاعات انتشار: سیزدهیمن کنفرانس مهندسی برق ایران، سال
تعداد صفحات: ۶
Many Researchers have widely investigated developing a mathematical model for generating artificial electrocardiogram (ECG) signals. In this paper we present a new comprehensive model for artificial ECG generation. Using a new neural network approach in a nonlinear dynamical system provides the ability of generating a wide range of ECG signals. In addition, using the Integral Pulse Frequency Modulator (IPFM) model incorporates the effects of sympathetic and parasympathetic activities in simulating the heart rate variability (HRV) signals. The inter–coupling between sympathetic and parasympathetic systems is also included. In addition to modelling the abnormalities associated with the shape of ECG, this model can easily model the HRV signals associated with the autonomic regularity of heart rate sicknesses. One of the uses of this model is for easy assessment of diagnostic ECG signal processing devices.<\div>

۱۲Asphaltene identification using intermolecular potential energy and nanostructural forces
نویسنده(ها): ، ، ،
اطلاعات انتشار: پنجمین کنگره بین المللی مهندسی شیمی، سال
تعداد صفحات: ۱۵
Heavy organic deposits remediation during petroleum production is a costly process and hamperes oil production operations. Asphaltene Precipitation in wells and reserviors has deterimental effects on the economics of oil production by reducing well production. In this work, the intermolecular potential energy of asphaltene complex has been calculated. Our objective is to observe and determine the surface structure of asphaltene micelles with explorer and discoverer scanning probe microscopes. The focus is to characterize their structure, dynamics, thermodynamics and to establish the relationship between these properties and petroleum fluid behavior. Quantum mechanics basics and statistical thermodynamics are applied to predict the potential energy and intermolecular forces of asphaltene molecules. The functional form of Potential energy and intermolecular forces are evaluted. Calculated data are compared to the proposed models. A dimensionless intermolecular potential energy function and also the forces are proposed. The validity of the results are checked by experimental data. The good agreement between one of the proposed models and the calculations is promising.<\div>

۱۳Gas–lift allocation optimization using generalized reduced gradient approach
نویسنده(ها): ، ، ،
اطلاعات انتشار: پنجمین کنگره بین المللی مهندسی شیمی، سال
تعداد صفحات: ۱۱
Continuous gas–lift is one of the most common artificial lift methods. High–pressure gas is injected into the tubing continuously, to lighten the oil column, which results in production enhancement. As a result of gas limitation it is impossible to make all the network wells produce at the maximum rate, hence the need to determine proper gas allocation. Gas allocation optimization is a nonlinear function maximization the decision variables of which are gas injection rates for each well, which are subject to the physical restrictions. In this work, Gas–lift performance curve (GLPC) is plotted and compared for different pressure drop correlations, by means of nodal analysis simulation. In this way, the most efficient correlation, especially for vertical two–phase flow was found to produce more precise pressure drop information. The generalized reduced gradient (GRG) method is also used as an efficient tool for network optimization to select the most proper gas allocation for each well.<\div>

۱۴Optimization of Pazanan Production Unit for Maximum Oil Recovery
نویسنده(ها): ، ،
اطلاعات انتشار: هشتمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۹
An intermediate pressure, called optimum separator pressure, was selected to maximize the oil volume accumulation in the stock – tank, in Pazanan production unit. This production unit produces 36000 bbl\day and it is located in southwestern Iran. Stage separation is a process in which gaseous and liquid hydrocarbons are flashed (separated) into vapor and liquid phases by two or more separators. The purpose of the
stage separation then is to reduce the pressure on the produced oil in steps so that more stock–tank oil recovery will result. If the separator pressure is high, large amounts of light components will remain in the liquid phase at the separator and will be lost along with other valuable components to the gas phase at the stock–tank. On the other hand if the pressure is too low, large amounts of light components will be separated from the liquid and they will attract substantial quantities of intermediates and heavier components so it is necessary to optimize separators pressure in winter and summer situation. Considerable gains could be realized by implementing of recommendations.<\div>

۱۵Phase Equilibria of R–22 (CHClF2) Hydrate in the presence of Acetone + Water
نویسنده(ها): ، ، ،
اطلاعات انتشار: هشتمین کنگره ملی مهندسی شیمی ایران، سال
تعداد صفحات: ۸
The effect of acetone on CHClF2 hydrate equilibrium conditions has been investigated. A full view equilibrium cell and associated equipment are designed, fabricated and used for this purpose. Adding acetone caused an increase of the equilibrium pressure. The equilibrium conditions were measured in the pressure range of 32 to 112 psia. The investigated concentrations of acetone in water were 2, 4, and 6 mole%. In contrast to
methane hydrate in the presence of acetone, the system of CHClF2 + acetone + water shows inhibition effect for all of the above concentration of acetone. The existing model for structure II hydrates in the ternary mixtures of methane + water + acetone has been applied for the above system. The measured dissociation temperatures have been compared with the results of this model.<\div>
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