Interference Coefficient Research Articles

A PRODUCTION SPLITTING MODEL OF HETEROGENEOUS MULTI-LAYERED RESERVOIRS WITH COMMINGLED PRODUCTION

Production splitting is the basis for a proper understanding of the development effect of reservoirs when multiple layers are commingled to produce, and it is a difficult part of the development evaluation of this type of reservoir. Reservoirs with multiple layers are usually developed through commingled production. However, due to interlayer interference, the total output of commingled production is lower than the sum of individual production of each subordinate layer. It's significant to clarify the interlayer interference mechanism during layers with commingled production, establish an accurate splitting model of the production from subordinate layers, split the commingled production into each subordinate layer, and effectively understand the production level and remaining potential of the subordinate layers during commingled production. It is expected to develop a theoretical basis for the rational and effective development of multi-layered commingled production reservoirs. In this paper, a combination of multi-tube parallel displacement experiments and numerical simulations of a multi-layered reservoir with commingled production is used to analyze the influence of factors such as permeability ratio, production pressure difference, and crude oil viscosity on the interlayer interference mechanism. According to the research results, the interference coefficient is firstly introduced on the basis of the theoretical production formula of seepage flow. The change rate of the oil production splitting coefficient at the stage when the water cut is more than 80% is also proposed, and the production splitting model of subordinate layers in heterogeneous reservoirs is established, considering multiple factors. Taking multi-layered Reservoir A with commingled production as an example, this model is used to split the production of commingled wells. Results show that interlayer interference can be reduced by decreasing the permeability ratio and high permeability laminar fluidity, and increasing the production pressure difference. When the water content is greater than 80%, the oil production segmentation coefficient of the layers with high permeability decreases sharply with the increase of the water content. For the low-permeable layer, the situation is just the opposite. At the same time, based on the study of the interlayer interference mechanism coupled with the oil well radial flow production formula, the interference coefficient and the oil production segmentation coefficient change ratio are introduced. The findings of this study can help develop a more accurate model for production of subordinate layers in heterogeneous multi-layered reservoirs. The established splitting model is carried out using the data from two wells and four subordinate layers in Reservoir A, indicating that the accuracy of the proposed model is close to 90%.

Analysis of the Induced Stress Fields Around Hydraulic Fractures Considering the Influence of Natural Fractures and Bedding Planes.

Natural fractures (NFs) and bedding planes (BPs) are well developed in shale reservoirs. The propagation of hydraulic fractures (HFs) and the opening of NFs and BPs can produce induced stress fields (ISFs) within the fracturing process, causing interference to the in situ stress field. Aiming at the "stress shadow" effect among HFs in horizontal wells, the calculation models of HFs, BPs, and NFs for induced stress distributions are established based on displacement discontinuity theory, which can quantitatively characterize the composite ISF of the three under different connecting states. In addition, the interference coefficient of stress intensity factor (ICSIF) is introduced to quantitatively evaluate the interference degree of the composite ISF to the propagation of HFs. The results show that: (1) the ISF forms a "tensile stress concentration zone" near the fracture surface to promote the HFs opening and a "compressive stress concentration zone" at the fracture tips to suppress the propagation of HFs; (2) the ISF forms an elliptical effective swept area around the fracture, which is affected by the propagation height of HFs, while NFs or BPs generate local disturbances to the ISF; (3) the in situ stress reverses in the swept area, and the stress reversal interval is related to the in situ stress difference, fracture propagation height, Poisson's ratio, fracture net pressure, and fracture spacing; (4) the reasonable fracture spacing and fracture propagation height of horizontal wells can be determined by the ICSIF. The study can provide theoretical guidance for optimizing the fracture spacing and promoting the uniform propagation of multiple fractures in staged fracturing of horizontal wells.

Performance Investigation of Airfoils for Axial Flow Fans in Low Solidity Cascades Operating at High Inlet Flow Angles

Abstract Axial flow fans are usually characterized by blade sections with low solidity and high inlet flow angles. Two main approaches are followed in the preliminary design phase, to take into account blade interaction effects: the use of available airfoil cascades data (or related correlations) and that of isolated airfoil data together with interference coefficients. The working conditions of low solidity airfoil cascades with highly tangential inflow are not widely studied in the literature, leaving the designer the possibility to rely on limited cascade data or often on the use of isolated airfoil data, with the assumption of negligible interference effects. A systematic investigation of the above working conditions for airfoil cascades is performed with Reynolds-averaged Navier–Stokes simulations. Three different airfoils are used to evaluate the influence of the design lift coefficient and maximum blade thickness. The results provide a better insight into the aerodynamic behavior of airfoil sections in such operating conditions, showing that interactions cannot be neglected. The use of metamodeling coupled with computational fluid dynamics (CFD) simulations is presented as a suitable tool for treating interference effects within the fan design process. The main findings of the present work can be used as a support for design choices as well as for developing design strategies both for the fan blades and for the airfoil sections.

Thin-interbedded reservoirs prediction based on seismic sedimentology

Interference of thin-interbedded layers in seismic reflections has great negative impact on thin-interbedded reservoirs prediction. To deal with this, two novel methods are proposed that can predict the thin-interbedded reservoirs distribution through strata slices by suppressing the interference of adjacent layer with the help of seismic sedimentology. The plane distribution of single sand bodies in thin-interbedded reservoirs can be clarified. (1) The minimum interference frequency slicing method, uses the amplitude-frequency attribute estimated by wavelet transform to find a constant seismic frequency with the minimum influence on the stratal slice of target layer, and then an optimal slice corresponding the constant frequency mentioned above can be obtained. (2) The superimposed slicing method can calculate multiple interference coefficients of reservoir and adjacent layers of target geological body, and obtain superimposed slice by weighted stacking the multiple stratal slices of neighboring layers and target layer. The two proposed methods were used to predict the distribution of the target oil layers of 6 m thick in three sets of thin-interbedded reservoirs of Triassic Kelamayi Formation in the Fengnan area of Junggar Basin, Northwestern China. A comparison with drilling data and conventional stratal slices shows that the two methods can predict the distribution of single sand bodies in thin-interbedded reservoirs more accurately.

Using Digital Models to Identify Hydrodynamic Interference Between Producing and Injection Wells to Improve Field Development Management Efficiency

Effective development of oil fields is impossible without reliable information on the degree of well interference. The interference between production and injection wells is evaluated using indicators that are commonly known as the interference coefficients or connectivity coefficients. There are a number of statistical, analytical, and predictive methods for hydrodynamic connectivity (interference) assessment. This paper focuses on a new approach designed to overcome the challenges related to the rational development of reserves and well interference assessment with building an improved hybrid material balance model. The purpose of the research was to evaluate various scenarios for well interference assessment, as well as to identify hydrodynamic communication between injection wells and specific producing wells for prompt decision-making to optimize the development system. The paper discusses the results of studies conducted on one field of Western Siberia, having a complex geological structure and high heterogeneity. Well interference coefficients were obtained as the result of the studies, which helped us to understand how the average proportion of water injected from a particular injection well effectively impacts the producing wells in question located in the immediate vicinity. The digital hybrid model was used to identify the injection wells that are hydrodynamically connected with producing wells, estimate the degree of their impact on the production performance of the latter, as well as monitor the dynamics of such influence for each well. Based on the analysis performed, some recommendations were made for improving the oil recovery factor in the oil fields and reducing development costs.

Rotor Strength Analysis of FeCo-Based Permanent Magnet High Speed Motor

To solve the problem of tension stress caused by centrifugal force and caused by high-speed operation of permanent magnet (PM) rotor, a FeCo-based PM rotor structure model is proposed. Based on the thick-walled cylinder theory, the uniform analytical calculation formulas of strain field, displacement field, and stress field of high-speed permanent magnet rotor are derived, and the stresses of FeCo-based PM and sleeve are obtained. The correctness of analytical calculation method (ACM) is verified by finite element method (FEM). Based on the derived analytical formula, the influence of static interference, sleeve thickness, rotating shaft, and PM thermal expansion coefficient on the strength of high-speed permanent magnet rotor is analyzed, and the mechanical design law of high-speed permanent magnet rotor is summarized. Alloy sleeves are usually fitted outside the high-speed permanent magnet rotor to protect the PM from damage. In order to ensure safe operation of PM rotor under hot rotating conditions, strength calculation and check of sleeve and PM must be carried out. Based on the characteristics of slender structure of high-speed rotor, a high-speed permanent magnet motor (HSPMM) with a rated power of 100 kW and a rated speed of 18,000 r/min was produced, and a continuous operation test was carried out to verify the validity of the above theoretical analysis.

Dynamic analysis of the e-SITR model for remote wireless sensor networks with noise and Sokol-Howell functional response

Wireless Sensor network (WSN) is used for a wide range of uses, including defense, healthcare, environmental tracking etc. In this work, we have formulated a Susceptible-infected-terminally infected-recovered (SITR) model to investigate the offensive worm dynamics in remote sensor networks utilizing Sokol-Howell functional response. The positive invariance and boundedness of the model have been investigated in the proposed work. In addition to that, the existence of possible equilibrium points with feasible conditions has been evaluated. The local stability of all equilibrium points and the global stability of the interior steady state of nodes are measured with the Rougth-Hurwitz criteria, Lasalle’s invariance principle, and Bendixson-Dulac criteria. The impact of noise on the proposed model is being investigated. The numerical imitations are carried out, which strengthens the diagnostic discoveries. Our numerical simulation reveals that growth rate, internode interference coefficients, and crashing rates are critical to the model's dynamics.

A FE study on the effect of interference fit and coefficient of friction on the micromotions and interface gaps of a cementless PEEK femoral component

The use of a more compliant material, such as polyetheretherketone (PEEK), for a cementless femoral component is a potential solution to prevent aseptic loosening caused by peri-prosthetic stress-shielding. Long-term fixation of a cementless femoral component is achieved by a proper primary fixation of the bone-implant interface, which is influenced by the interference fit and frictional properties of the implant surface. This computational study investigates the sensitivity of micromotions and interface gaps of a cementless PEEK femoral component to the interference fit and coefficient of friction. 24 finite element models of the femur and femoral component were created with variations in implant material, interference fit and coefficient of friction. Peak loads of a jogging activity were applied on the models. Micromotions and interface gaps were both sensitive to the interference fit, coefficient of friction and implant material. Besides the implant material, the micromotions and interface gaps of the implant were most sensitive to the interference fit. Compared to the cobalt-chrome (CoCr) femoral component, the PEEK femoral component generated higher micromotions and interface gaps when equal interference fit and friction values were applied. However, increasing the interference fit and friction of the PEEK component resulted in micromotion values comparable with the CoCr component. This result leads to possibilities using cementless PEEK femoral components.

Design of Open-Ended Structure Wideband PCB Rogowski Coil Based on New Winding Method

Compared with the traditional Rogowski coil, printed circuit board (PCB) Rogowski coil has the advantages of high measurement accuracy, simple manufacturing process and low cost. It has become an important device in current measurement. However, the existing PCB Rogowski coils are mostly closed, and the open-ended structure PCB Rogowski coils are susceptible to external magnetic field interference. This paper proposes an open-ended structure PCB Rogowski coil based on a new winding method, so that the two open-ended PCB Rogowski coils are evenly distributed when closed, while improving the coil’s immunity to external magnetic fields based on the winding method of equal area of the de-wired and loop. In addition, this paper uses the hybrid integration circuit and the back-end matching method to achieve the broadband measurement performance of the sensor. Finally, the experimental results show that the mutual inductance difference between the closed and open-ended structure PCB Rogowski coil is less than 0.5% under the same wiring mode. Under the equivalent current interference at 50 mm from the measured current, the maximum interference coefficient of the open-ended structure coil is 1.45%; in sine sweep and pulse current test conditions, the frequency band is 34 Hz–3.5 MHz.

Multi-Gas Detection System Based on Non-Dispersive Infrared (NDIR) Spectral Technology.

Automobile exhaust gases, such as carbon dioxide (CO2), carbon monoxide (CO), and propane (C3H8), cause the greenhouse effect, photochemical smog, and haze, threatening the urban atmosphere and human health. In this study, a non-dispersive infrared (NDIR) multi-gas detection system consisting of a single broadband light source, gas cell, and four-channel pyroelectric detector was developed. The system can be used to economically detect gas concentration in the range of 0–5000 ppm for C3H8, 0–14% for CO, and 0–20% for CO2. According to the experimental data, the concentration inversion model was established using the least squares between the voltage ratio and the concentration. Additionally, the interference coefficient between different gases was tested. Therefore, the interference models between the three gases were established by the least square method. The concentration inversion model was experimentally verified, and it was observed that the full-scale error of the sensor changed less than 3.5%, the detection repeatability error was lower than 4.5%, and the detection stability was less than 2.7%. Therefore, the detection system is economical and energy efficient and it is a promising method for the analysis of automobile exhaust gases.

Error Control on Mobile Station Sides in Collaborative Multiple-Input Multiple-Output Systems

Collaboration between mobile stations (MSs) may lead to a new form of wireless communication. Collaboration on MS sides considerably improves signal detection performance, especially for multiple-input multiple-output (MIMO) transmission systems. In this study, a novel detector collaboration system is proposed to reduce the traffic volume on inter-MS collaboration links. Multiple MSs in the immediate vicinity are used to collaboratively decode the MIMO signals received from a base station. Furthermore, we consider a distributed detection system, in which multiple detection MSs decode the MIMO signals independently. Multiple decision results are exploited to improve the error performance. Residual interference coefficients were used to finalize the decision results. The error ratio performance and the traffic volume over collaboration wireless links were compared with those of two combining schemes through computer simulations and field experiments. The results revealed that the proposed error control scheme on mobile station sides offers a better tradeoff between the error performance and the traffic volume on the collaboration wireless links.

Fano resonance of optical phonons in a multilayer graphene stack

We studied Fano interference between the Raman spectrum of G-band phonons and electron continuum in a multilayer graphene stack. The thickness and power dependencies of the Fano interference coefficient ∣1/q∣ in the G-mode, where q is the Fano asymmetry parameter, were spatially visualized and analyzed using the Gaussian-convoluted Breit–Wigner–Fano function. The estimated ∣1/q∣ decreases with an increase in the layer number and laser power in the low-power region at least for monolayer, bilayer, and trilayer graphene. In the higher-power region, ∣1/q∣ increases with power only for monolayer graphene. The observed behaviors of ∣1/q∣ reflect the phase difference of Raman signals from the electron continuum and G-band and possibly originate from changes in the electronic relaxation time and the Fermi level of graphene owing to the laser heating of the sample.

Adaptive Turbo Equalization for Nonlinearity Compensation in WDM Systems

In this paper, the performance of adaptive turbo equalization for nonlinearity compensation (NLC) is investigated. A turbo equalization scheme is proposed where a recursive least-squares (RLS) algorithm is used as an adaptive channel estimator to track the time-varying intersymbol interference (ISI) coefficients associated with inter-channel nonlinear interference (NLI) model. The estimated channel coefficients are used by a MIMO $2\times 2$ soft-input soft-output (SISO) linear minimum mean square error (LMMSE) equalizer to compensate for the time-varying ISI. The SISO LMMSE equalizer and the SISO forward error correction (FEC) decoder exchange extrinsic information in every turbo iteration, allowing the receiver to improve the performance of the channel estimation and the equalization, achieving lower bit-error-rate (BER) values. The proposed scheme is investigated for polarization multiplexed 64QAM and 256QAM, although it applies to any proper modulation format. Extensive numerical results are presented. It is shown that the scheme allows up to 0.7 dB extra gain in effectively received signal-to-noise ratio (SNR) and up to 0.2 bits/symbol/pol in generalized mutual information (GMI), on top of the gain provided by single-channel digital backpropagation.

Monitoring of Mutual Interference Behavior of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) over 45 Generations of Rearing on Angoumois Grain Moth.

Trichogramma brassicae (Bezdenko) is one of the most common species of natural enemies used in augmentative biological control programs in many countries. Understanding of the foraging behavior of a parasitoid can help us to improve its performance under field conditions. This study is the first assessment of trends in mutual interference behavior of T. brassicae under long-term mass rearing (over 45 generations) on a common factitious host, Sitotroga cerealella (Olivier). Our results revealed that the total parasitism rate of T. brassicae reared on S. cerealella eggs was significantly affected by parasitoid densities and number of generations under continuous rearing. Also, parasitoid density and number of generations in rearing had significant effects on the per capita parasitism rate. Meanwhile, per capita searching efficiencies were different in sequential generations and at different densities. The number of hosts parasitized per parasitoid decreased on day 1 of the experiment with increasing parasitoid density, showing the effect of mutual interference. The linear regression between the natural logarithm of per capita searching efficiency and the natural logarithm of parasitoid density showed an inverse relationship. While the m (interference coefficient) values increased, the Q (quest constant) values had a decreasing trend over 45 generations. The highest (- 0.167) and lowest (- 0.242) values of m were observed in G45 and G5, respectively. Accordingly, G5 and G45 had the highest (0.053) and lowest (0.023) Q values, respectively. Thus, it seems the negative effects of mutual interference decreased over generations.

Torque capacity of the multilayer interference fit based on a friction coefficient prediction model

This paper proposes the theoretical model of a multilayer interference fit and gives out the relational expression between radial interference and friction coefficient. Taking the typical wind turbine's shrink disk of a three-layer interference fit structure as an example, special experimental equipment is developed to test the torque capacity. Based on experimental results and the theoretical model, the mathematical expressions of radial interference and assembly stroke for friction coefficient are obtained by polynomial fitting, and the prediction model of friction coefficient is established. The three-dimensional finite element model of a shrink disk is constructed by applying the friction coefficient prediction model. With the mathematical expressions of radial interference and assembly stroke for the torque capacity, the rules of main dimension parameters and torque capacity are analyzed. The maximum relative error between experiment and simulation is 8.2%, which shows the feasibility of finite element simulation. The results of our study have certain guidance for the prediction of friction coefficient and the manufacture of the multilayer interference fit.

A comprehensive picture of foraging strategies of Neoseiulus cucumeris and Amblyseius swirskii on western flower thrips.

This study evaluated the potential of Neoseiulus cucumeris Oudemans and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) for controlling western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), by determining the functional response, numerical response, prey switching and mutual interference behaviors of the predators. A type II functional response was detected for two predator species fed on WFT first instars. The attack rate was higher for A. swirskii than N. cucumeris, but the handling time of N. cucumeris was shorter. For two predator species, numerical response was affected by both prey density and oviposition time. The per capita searching efficiencies of the two predators decreased significantly with increasing predator densities. The interference coefficient for A. swirskii was less than that of N. cucumeris. Although N. cucumeris switched from feeding on WFT first instars to feeding on second instars, this behavior was not observed in A. swirskii. Comparison of the two predator species foraging behaviors indicated optimal performance by A. swirskii at lower F. occidentalis densities. N. cucumeris was found to perform optimally at relatively higher prey densities. Moreover, N. cucumeris could be more effective in stabilizing the predator-prey system by switching behavior compared with A. swirskii. At higher predator densities, A. swirskii seemed to be an effective agent owing to its reduced intraspecific competition compared with N. cucumeris. Findings from this study will be useful in selecting appropriate agents and developing effective biocontrol programs to control WFT. © 2021 Society of Chemical Industry.

Parametric Study of Magnus Wind Turbine with Spiral Fins using BEM Approach

The aim of this work is to carry out an aerodynamic analysis to assess the power and identify the characteristics of the horizontal axis Magnus type wind turbine with spiral fins. A parametric study is achieved to analyze the effects of the different influence parameters such as the turbine tip speed ratio, the cylinder spinning ratio, the blade aspect ratio and the cylinder hub-tip ratio. The analysis approach adopted in this study is the Blade Element Momentum BEM using the experimental lift coefficient data for the configuration of spinning cylinders with spiral fins. In this analysis, losses are not taken in consideration. Both axial and angular interference coefficients are evaluated for this type of wind turbine. The former is assessed by solving a quadratic equation and the latter is calculated from a classic formulation including the term of spinning. An iterative process is followed to achieve this task. Concerning the obtained results, the aerodynamic characteristics of the Magnus wind turbine, analyzed in this study, provide some elucidation to lead a successful preliminary design of this novel type of machine.

Unfolding WMMSE Using Graph Neural Networks for Efficient Power Allocation

We study the problem of optimal power allocation in a single-hop ad hoc wireless network. In solving this problem, we depart from classical purely model-based approaches and propose a hybrid method that retains key modeling elements in conjunction with data-driven components. More precisely, we put forth a neural network architecture inspired by the algorithmic unfolding of the iterative weighted minimum mean squared error (WMMSE) method, that we denote by unfolded WMMSE (UWMMSE). The learnable weights within UWMMSE are parameterized using graph neural networks (GNNs), where the time-varying underlying graphs are given by the fading interference coefficients in the wireless network. These GNNs are trained through a gradient descent approach based on multiple instances of the power allocation problem. We show that the proposed architecture is permutation equivariant, thus facilitating generalizability across network topologies. Comprehensive numerical experiments illustrate the performance attained by UWMMSE along with its robustness to hyper-parameter selection and generalizability to unseen scenarios such as different network densities and network sizes.

Subgrade reaction modulus of rock masses under the load of single and multiple footings

ABSTRACT Subgrade reaction modulus is an essential parameter in the structural design of footings. Determination of this parameter is difficult, especially in rock masses containing an irregular distribution of discontinuities. In this paper, the subgrade reaction modulus of rock masses obeying Hoek-Brown failure criterion was investigated. It was assumed that the rock masses are under the pressure of a single isolated footing and also two adjacent strip footings. The subgrade reaction modulus was determined from the pressure-settlement curve of the rock masses. This study’s results were presented in two forms, which include the subgrade reduction factor and the interference coefficient. The obtained results show that the subgrade reaction modulus of rock masses may be smaller than 50% of intact rocks. Likewise, based on the distance between the multiple footings, the subgrade reaction modulus may be in the range of 0.7 to 1.3 times the subgrade reaction modulus in the case of a single isolated footing.

Optimization of particle swarm algorithm and its usage in calculation of hydrogeological parameter

In order to improve the accuracy, sensitivity, and convergence, the particle swarm optimization (PSO) algorithm is optimized and applied in the calculation of hydrogeological parameters to improve the accuracy of the hydrogeological model. The sensitivity and accuracy of the algorithm are improved through derivation of the appropriate value of the particles. Based on convergency analysis of this algorithm with the three intelligent optimization algorithms (Sphere function, Rosenbrock function, and Griewank function), the convergence of the algorithm is analyzed through different intelligently optimized algorithms. At the same time, the accuracy is validated through comparison between the optimized and unoptimized particle swarm algorithm as well as the actually observed hydrogeological data, and the sensitivity of the water conductivity coefficient and water storage coefficient under the algorithm is analyzed. The results show that the calculated value of the optimized PSO algorithm is very close to the theoretical value 0 of the intelligent optimization algorithm Sphere function and the theoretical value 1 of the Rosenbrock function as well as the theoretical value 1 of the Griewank function. The results reveal that the calculation results are very close to the theoretical value in the intelligent optimization algorithm test of optimized particle swarm algorithm; the maximum absolute error between the calculated value and the observed value of the optimized particle swarm algorithm is 0.011, and the maximum relative error of which is 8.1%; the maximum absolute error between the calculated value of particle swarm algorithm and the observed value is 0.021, and the maximum relative error reaches 29.1%; the number of iterations of the optimized particle swarm algorithm is 87 on average, while it of the unoptimized particle swarm algorithm is 450, reaching the optimal value. In addition, the optimized PSO algorithm has a standard function of 0.00659, which is significantly smaller than that of the PSO algorithm of 0.00684. When the interference coefficient is −20%~20%, the water conductivity coefficient and water storage coefficient are in negative phase with the drop depth of the aquifer. It suggests that the optimized particle swarm optimization algorithm has high accuracy and convergence, and its sensitivity of water conductivity coefficient and sensitivity of water storage coefficient are both good, which can provide a reliable algorithm basis for the construction of hydrogeological model and the establishment of aquifer parameters.