Transmissibility Coefficients Research Articles

Effect of Transmission and Vaccination on Time to Dominance of Emerging Viral Strains: A Simulation-Based Study.

We studied the effect of transmissibility and vaccination on the time required for an emerging strain of an existing virus to dominate in the infected population using a simulation-based experiment. The emergent strain is assumed to be completely resistant to the available vaccine. A stochastic version of a modified SIR model for emerging viral strains was developed to simulate surveillance data for infections. The proportion of emergent viral strain infections among the infected was modeled using a logistic curve and the time to dominance (TTD) was recorded for each simulation. A factorial experiment was implemented to compare the TTD values for different transmissibility coefficients, vaccination rates, and initial vaccination coverage. We discovered a non-linear relationship between TTD and the relative transmissibility of the emergent strain for populations with low vaccination coverage. Furthermore, higher vaccination coverage and high vaccination rates in the population yielded significantly lower TTD values. Vaccinating susceptible individuals against the current strain increases the susceptible pool of the emergent virus, which leads to the emergent strain spreading faster and requiring less time to dominate the infected population.

Tests of selected anti-vibration gloves available on the Polish market

The authors of the paper conducted tests of anti-vibration gloves available on the market (17 types) in accordance with the methodology of the EN ISO 10819: 2013 standard. The main purpose of these studies was to verify the data provided by manufacturers in product specifications and user manuals. Based on the determined values of the vibration transmissibility coefficients, it was found that, despite the certificates held by all the tested gloves, as many as 6 types do not meet the minimum requirements for anti-vibration gloves, and two types achieve properties on the verge of meeting these requirements. Two types of gloves (despite the certificate) did not show any significant vibration damping in the whole tested frequency range. The obtained test results indicate the need to verify the anti-vibration properties of the available certified gloves from unverified suppliers. It also seems necessary to assess the effectiveness of protection of anti-vibration gloves in the conditions of their actual use.

Integro-differential approach for modeling the COVID-19 dynamics - Impact of confinement measures in Italy

The COVID-19 pandemic has overwhelmed the life and security of most of the world countries, and especially of the Western countries, without similar experiences in the recent past. In a first phase, the response of health systems and governments was disorganized, but then incisive, also driven by the fear of a new and dramatic phenomenon. In the second phase, several governments, including Italy, accepted the doctrine of “coexistence with the virus” by putting into practice a series of containment measures aimed at limiting the dramatic sanitary consequences while not jeopardizing the economic and social stability of the country. Here, we present a new mathematical approach to modeling the COVID-19 dynamics that accounts for typical evolution parameters (i.e., virus variants, vaccinations, containment measurements). Reproducing the COVID-19 epidemic spread is an extremely challenging task due to the low reliability of the available data, the lack of recurrent patterns, and the considerable amount and variability of the involved parameters. However, the adoption of fairly uniform criteria among the Italian regions enabled to test and optimize the model in various conditions leading to robust and interesting results. Although the regional variability is quite large and difficult to predict, we have retrospectively obtained reliable indications on which measures were the most appropriate to limit the transmissibility coefficients within detectable ranges for all the regions. To complicate matters further, the rapid spread of the English variant has upset contexts where the propagation of contagion was close to equilibrium conditions, decreeing success or failure of a certain measure. Finally, we assessed the effectiveness of the zone assignment criteria, highlighting how the reactivity of the measures plays a fundamental role in limiting the spread of the infection and thus the total number of deaths, the most important factor in assessing the success of epidemic management.

NEW METHOD FOR SPLITTING PRODUCTION AND INJECTION IN JOINT WELLS USING MODIFIED CRM MODEL

Operating several oil-bearing facilities with a single grid of wells, the problem of dividing oil and liquid production rates by facilities is urgent. Known engineering techniques based on reservoir transmissibility coefficients and effective oil-saturated thickness do not take into account dynamic factors. The use of hydrodynamic models (HDM) is time-consuming, and the results depend significantly on the used a priori hypotheses about the geological structure of objects and the properties of fluids. Thus, there is a practical need for an analytical tool that would rely on the most reliable and available data and would allow solving the problem of separating the volumes of produced fluid and injected water with sufficient accuracy. Such a tool should take into account the dynamics of changes in reservoir pressure and have a low (compared to the hydrodynamic model) need for computing resources. A promising candidate for the role of such a tool is the CRMP-ML6 model — a fundamentally new author’s modification of the previously known CRMP model. The CRMP model is a functional dependence of the well fluid flow rate on the injectivity of the surrounding injection wells. The unknown parameters of this dependence are determined in such a way as to minimize the discrepancy between the simulated and actual values of production rates at the selected date interval. Fundamentally new features of the CRMP-ML6 model are the regularization of the problem through the use of a priori information on the permeability of reservoirs in the vicinity of production wells and the requirement for the proximity of reservoir pressures calculated using the material balance model and from the Dupuis equation. To assess the performance of the new model, a number of numerical simulation experiments were carried out, and the simulation results were compared with the HDM. The possibility of the CRMP-ML6 model is demonstrated to take into account the dynamic separation of production and injection, taking into account additional constraints and a priori information, and while meeting all the requirements for models of the CRM family.

Development of a fast EoS based compositional model for three-phase core flooding

Compositional simulators are of great importance to model core flow experiments and enhanced oil recovery processes. In the present study, a semi-implicit, three dimensional EoS-based formulation is developed for modeling and simulation of core-flooding process. The model treats three-phase flow in cylindrical coordinates with no need to use an iterative numerical method. Overall composition, pressure and water saturation are calculated implicitly for each grid block. Using this approach, a linear set of equations with constant coefficients would be solved at each time step. It is assumed that there is no mass transfer between hydrocarbon phases and water phase. In addition, a new technique has been suggested to calculate transmissibility coefficients in each direction, which is a major problem in compositional modeling. Each transmissibility coefficient is divided into two general parts which are treated differently. The first part is constant and the second part is time-dependent. This model yields a robust and fast calculation procedure, which is validated using Eclipse simulation results. Simulation of several miscible flooding processes were performed using Eclipse core-flood models in order to compare the results with the developed in-house model. Results are matched reasonably while the computing time is considerably decreased using the in-house model. It is shown that using second Stone’s relative permeability model and Advanced Peng–Robinson Equation of State, best results are achieved with an average absolute relative deviation of 7.7% from Eclipse results for ultimate recovery factor. In addition, sensitivity analysis has been performed on several input data including time-step size and block number. Results show that in a reasonable range of these parameters, convergence problems are not encountered. We have developed an in-house simulator based on our model, which can be a basis for other compositional simulation purposes. In addition to decreasing computing time, convergence problems encountered in most implicit techniques would be avoided as well.

Convergence of a positive nonlinear control volume finite element scheme for an anisotropic seawater intrusion model with sharp interfaces

AbstractWe study a sharp interface model in the context of seawater intrusion in an anisotropic unconfined aquifer. It is a degenerate parabolic system with cross‐diffusion modeling the flow of fresh and saltwater. We study a nonlinear control volume finite element scheme. This scheme ensures the nonnegativity of the discrete solution without any restriction on the transmissibility coefficients. Moreover, it also provides a control on the entropy. The existence of a discrete solution and the convergence of this scheme are obtained, based on nonlinear stability results.

A note on transgenerational epigenetics affecting egg quality traits in meat-type quail

ABSTRACT1. The aim of the following experiment was to estimate transgenerational epigenetic variance for egg quality traits using genealogical and phenotypic information in meat-type quail. Measured traits included egg length (EL) and width (EWD), albumen weight (AW), shell weight (SW), yolk weight (YW) and egg weight (EW).2. A total of 391 birds were evaluated for egg quality by collecting a sample of one egg per bird, during three consecutive days, starting on the 14th d of production. Analyses were performed using mixed models including the random epigenetic effect. Variance components were estimated by the restricted maximum likelihood method. A grid-search for values for the auto-recursive parameter (λ) was used in the variance components estimation. This parameter is directly related to the reset (v) and epigenetic transmissibility (1 − v) coefficients.3. The epigenetic effect was not significant for any of the egg quality traits evaluated. Direct heritability estimates for egg quality traits ranged in magnitude from 0.06 to 0.33, whereby the higher estimates were found for AW and SW. Epigenetic heritability estimates were low and close to zero (ranging from 0.00 to 0.07) for all evaluated traits.4. The current breeding strategies accounting for additive genetic effect seem to be suitable for egg quality traits in meat-type quail.

Convergence of a positive nonlinear Control Volume Finite Element scheme for solving an anisotropic degenerate breast cancer development model

In this paper, a nonlinear control volume finite element (CVFE) scheme for solving an anisotropic degenerate breast cancer development model is introduced and analyzed. This model includes both ordinary differential equations and convection–diffusion–reaction equations modeling the stepwise mutations from a normal breast stem cell to a tumor cell. The diffusion term, which generally involves an anisotropic and heterogeneous diffusion tensor, is discretized on a dual mesh by means of the piecewise linear conforming finite element method and using the Godunov scheme to approximate the diffusion fluxes provided by the conforming finite element reconstruction. The other terms are discretized using a nonclassical upwind finite volume scheme on the dual mesh, where the dual volumes are constructed around the vertices of the original mesh. This technique ensures the positivity and boundedness of discrete solutions without any restriction on the diffusion tensor nor the transmissibility coefficients. The convergence of the scheme is proved, only supposing the shape regularity condition for the original mesh and using a priori estimates as well as the Kolmogorov relative compactness theorem. The proposed scheme is robust, locally conservative, efficient, and stable, which is confirmed by numerical experiments over a general mesh.

Analysis of multi-layered commingled and compartmentalized gas reservoirs

The evaluation and performance prediction of multi-layered compartmentalized gas systems can be difficult. This is mostly due to the uncertainties related to production allocation either within each commingled well or between interrelated reservoir compartments. This paper presents a model that can provide reliable estimates of the total gas in place for multi-layered commingled and compartmentalized reservoirs. The model is also capable of generating prediction profiles for every well in the production system in addition to forecasting individual layers production for each compartment. The proposed model is based on coupling the layered stabilized flow model for material balance calculation in commingled systems with communicating reservoir model that is used as material balance tool for compartmentalized gas reservoirs. The model has the flexibility to be applied for history matching and prediction purposes. In history matching, the model solves the equations simultaneously using optimization routine to find the best parameters of original gas in place (OGIP), deliverability coefficients and compartment transmissibility coefficients. The model requires the knowledge of initial reservoir pressure in every compartment, some rate production history and bottom-hole flowing pressures. The model can also utilize additional information such as shut-in pressures per layer, repeat formation tester and production logging tool measurements (if available) to improve the history match. For prediction, the model uses the estimated parameters (compartment OGIP, transmissibility coefficients between compartments and flow parameters for each layer) to calculate the production rates and reservoir pressures for every well/tank based on a provided bottom-hole flowing pressure. The model was verified against a commercial reservoir simulator for several synthetic cases. The model was also applied on different field cases to estimate OGIP and flow coefficients for every layer as well as compartment transmissibility coefficients. Moreover, calculation of cumulative gas transferred across the communicating reservoirs allows detection of poorly drained compartments, which could be included in future redevelopment plans.

Positive nonlinear CVFE scheme for degenerate anisotropic Keller-Segel system

In this paper, a nonlinear control volume finite element (CVFE) scheme for a degenerate Keller--Segel model with anisotropic and heterogeneous diffusion tensors is proposed and analyzed. In this scheme, degrees of freedom are assigned to vertices of a primal triangular mesh, as in finite element methods. The diffusion term which involves an anisotropic and heterogeneous tensor is discretized on a dual mesh (Donald mesh) using the diffusion fluxes provided by the conforming finite element reconstruction on the primal mesh. The other terms are discretized using a nonclassical upwind finite volume scheme on the dual mesh. The scheme ensures the validity of the discrete maximum principle without any restriction on the transmissibility coefficients. The convergence of the scheme is proved under very general assumptions. Finally, some numerical experiments are carried out to prove the ability of the scheme to tackle degenerate anisotropic and heterogeneous diffusion problems over general meshes.

Monotone multiscale finite volume method

The MultiScale Finite Volume (MSFV) method is known to produce non-monotone solutions. The causes of the non-monotone solutions are identified and connected to the local flux across the boundaries of primal coarse cells induced by the basis functions. We propose a monotone MSFV (m-MSFV) method based on a local stencil-fix that guarantees monotonicity of the coarse-scale operator, and thus, the resulting approximate fine-scale solution. Detection of non-physical transmissibility coefficients that lead to non-monotone solutions is achieved using local information only and is performed algebraically. For these ‘critical’ primal coarse-grid interfaces, a monotone local flux approximation, specifically, a Two-Point Flux Approximation (TPFA), is employed. Alternatively, a local linear boundary condition can be used for the dual basis functions to reduce the degree of non-monotonicity. The local nature of the two strategies allows for ensuring monotonicity in local sub-regions, where the non-physical transmissibility occurs. For practical applications, an adaptive approach based on normalized positive off-diagonal coarse-scale transmissibility coefficients is developed. Based on the histogram of these normalized coefficients, one can remove the large peaks by applying the proposed modifications only for a small fraction of the primal coarse grids. Though the m-MSFV approach can guarantee monotonicity of the solutions to any desired level, numerical results illustrate that employing the m-MSFV modifications only for a small fraction of the domain can significantly reduce the non-monotonicity of the conservative MSFV solutions.

Rate decline analysis of multiple fractured horizontal well in shale reservoir with triple continuum

Multiple fractured horizontal well (MFHW) is widely applied in the development of shale gas. To investigate the gas flow characteristics in shale, based on a new dual mechanism triple continuum model, an analytical solution for MFHW surrounded by stimulated reservoir volume (SRV) was presented. Pressure and pressure derivative curves were used to identify the characteristics of flow regimes in shale. Blasingame type curves were established to evaluate the effects of sensitive parameters on rate decline curves, which indicates that the whole flow regimes could be divided into transient flow, feeding flow, and pseudo steady state flow. In feeding flow regime, the production of gas well is gradually fed by adsorbed gases in sub matrix, and free gases in matrix. The proportion of different gas sources to well production is determined by such parameters as storability ratios of triple continuum, transmissibility coefficients controlled by dual flow mechanism and fracture conductivity.

Controller Design for Convoluted Air Spring System Controlled Suspension

This paper focuses on the analysis and controlling automotive vibration using semi-active air spring suspension system by implementing fuzzy and Proportional-Integral derivative (PID) controllers for light vehicles. Due to low transmissibility coefficients and their ability to varying the force generated depends on load capacities the air spring is modelled as an actuator. The dynamic behavior of semi active actuator controlled is contrasted with passive suspension under single bump, double bump and random road profile. The performance of air spring controlled suspension has been investigated. Results show that the fuzzy controller gives optimized results.

On the efficacy of a control volume finite element method for the capture of patterns for a volume-filling chemotaxis model

In this paper, a control volume finite element scheme for the capture of spatial patterns for a volume-filling chemotaxis model is proposed and analyzed. The diffusion term, which generally involves an anisotropic and heterogeneous diffusion tensor, is discretized by piecewise linear conforming triangular finite elements (P1-FEM). The other terms are discretized by means of an upstream finite volume scheme on a dual mesh, where the dual volumes are constructed around the vertices of each element of the original mesh. The scheme ensures the validity of the discrete maximum principle under the assumption that the transmissibility coefficients are nonnegative. The convergence analysis is based on the establishment of a priori estimates on the cell density, these estimates lead to some compactness arguments in L2 based on the use of the Kolmogorov compactness theorem. Finally, we show some numerical results to illustrate the effectiveness of the scheme to capture the pattern formation for the mathematical model.

CONDITIONING ELECTRONICS IN A SELF-POWERED VIBRATION REDUCTION SYSTEM: EXPERIMENTAL TESTING

The paper summarises the results of laboratory testing of a vibration reduction system with energy harvesting capability, implemented in an 2 DOF mechanical application. The vibration reduction system comprises a commercially available RD-1005-3 type magnetorheological (MR) damper and an electromagnetic energy transducer (EPE) executing the reciprocating motion. The aim of the experiment was to compare the performance of the vibration reduction with two types of power conditioning systems and that in which the MR damper coil is fed directly with energy generated by EPE. Frequency characteristics are provided showing the plots of transmissibility coefficients, MR damper force, voltage generated by EPE, current intensity in the MR damper control coil, supplied electric power and mechanical power dissipated by the damper.

A multi-resolution multiscale finite volume method for simulation of fluid flows in heterogeneous porous media

This paper presents an extension of the multiscale finite volume (MsFV) method to multi-resolution coarse grid solvers for single phase incompressible flows. To achieve this, a grid one level coarser than the coarse grids used in the MsFV method is constructed and the local problems are redefined to compute the basis and correction functions associated with this new grid. To construct the coarse-scale pressure equations, the coarse-scale transmissibility coefficients are calculated using a new multi-point flux approximation (MPFA) method. The estimated coarse-scale pressures are utilized to compute the multiscale pressure solution. Finally a reconstruction step is performed to produce a conservative velocity field which is used to solve the transport equations. The computational cost of the proposed method is compared with that of the MsFV method and the relevant time complexity formulas are given. Several two-dimensional test cases with permeability fields ranging from two-scale to multi-scale problems are solved. The performance of the proposed method in handling problems with shale layers or discrete fractures is assessed. Also, a number of layers from the tenth SPE comparative study problem are used to examine general abilities of the method when facing realistic reservoir problems. The results are compared with fine-scale reference solutions to assess the accuracy of the proposed method.

Transverse Strain Effects on the Measurement of the Thermal Expansion of Composite Structure Using Surface-Mounted Fiber Bragg Grating Sensors

The effects of transverse strain on the wavelength shifts of surface-mounted fiber Bragg grating (FBG) sensors are investigated. A new FBG model including the concept of strain transmissibility coefficients along the longitudinal and transverse directions of the sensors is proposed. The finite element method is applied to obtain the strain transmissibility coefficients between the FBG sensor and surface of the base structure. The wavelength shifts of each FBG sensor are calculated with respect to the assumed thermal strain condition of the base structures; the estimated strains by the proposed FBG model are compared with the results from conventional FBG model. The numerical results show that the surface strains of the composite structure can be predicted well using the proposed FBG model, while the conventional FBG model results in a larger error when the transverse strain of the base structure is much larger than longitudinal strain of the base structure, as in composite structures under thermal loadings.

Verification of damped cable system performance in the seismic rehabilitation of buildings

The performance capacities of the damped cable system are evaluated by the results of an experimental campaign developed on a full-scale three-story reinforced concrete structure retrofitted by this innovative protective technology. The experimental activity, carried out as part of a European Community funded Research Project, consisted of a repeated series of forced vibration tests, which offered a first realistic verification of the system response capabilities. This provided essential information on the on-site behaviour of the assembled system components, among which were cable connections with fluid viscous spring-dampers and story beams. The dynamic test results, elaborated in terms of equivalent transmissibility coefficients, energy dissipated by the spring-dampers and the entire structure, relevant energy ratios, and equivalent viscous damping coefficients, showed a significant improvement of structural performance in rehabilitated conditions, as well as a satisfactory correlation with design predictions. The analytical model of the structure, properly calibrated on the experimental data, was also used for a numerical seismic investigation, which confirmed the high degree of protection guaranteed by the examined technology.

An Introduction to Multipoint Flux Approximations for Quadrilateral Grids

Control-volume discretizations using multipoint flux approximations (MPFA) were developed in the last decade. This paper gives an introduction to these methods for quadrilateral grids in two and three dimensions. The introduction is kept on a basic level, and a brief summary to more advanced results is given. Only the O-method with surface midpoints as continuity points is discussed. Flux expressions are derived both in physical and in curvilinear space. Equations for calculation of the transmissibility coefficients are given, and an explicit solution is shown for constant coefficients. K-orthogonality, stability and monotonicity are discussed, and an iterative solution technique is presented. Two numerical examples close the paper.

Determination of the oxygen transmissibility and permeability of hydrogel contact lenses

To test the validity of the method of stacked hydrogel contact lenses to obtain the oxygen permeability and transmissibility coefficients of the lenses, the coefficients of one low hydration (38% water) and two high hydration (55 and 58% water) hydrogel contact lenses stacked one to five on an oxygen electrode were determined. From the oxygen diffusion through the lenses, the current intensity in the stationary state was determined, and from this the “instrument” the oxygen transmissibility was obtained. The permeability coefficients of the lenses, corrected for edge effects, were obtained from the slope of the plot of the reciprocal of the transmissibility coefficients versus the lens thicknesses. The oxygen permeability and transmissibility coefficients of the lenses obtained neglected the boundary layers resistance between the stacked lenses and, therefore, these are not the “true” coefficients. This article compares the “apparent” oxygen permeability coefficients of the hydrogel contact lenses, obtained by others, with the “true” oxygen permeability coefficients obtained with a corrected equation that takes into account the boundary layers between the stacked lenses. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 321–327, 1999