Pertinent System Parameters Research Articles

An Adjoint Sensitivity Model for Radionuclide Transport in Heterogeneous Discrete Fractured Porous Formation in Steady‐State Regime

The development of the adjoint state method for the system of partial differential equations (PDEs) describing radionuclide transport in heterogeneous discrete fractured porous media in steady-state regime is presented in this study for both continuous and discrete adjoint approaches. The continuous adjoint approach has its own advantage in the sense that the adjoint system can be derived in terms of PDEs which can be solved analytically for specific performance measures. These PDEs can then be used to obtain a physical interpretation of the adjoint state functions. The discrete adjoint approach permits a simpler mathematical treatment based on the use of the same matrix (or its transpose) of the linear system of the discretized transport equations referring to from hereon as the forward problem. Analytical solutions for both the forward problem and its associated adjoint problem have been derived for radionuclide transport in layered formations including a fracture using an analytical inversion of tridiagonal matrices. A set of 14 formulas of sensitivity coefficients with respect to pertinent system parameters has been derived and presented in integral forms. Analytical results have been compared with numerical results and have shown excellent agreements. The discrete adjoint approach has been coupled with the differential sensitivity analysis method and applied to a real field case involving the performance assessment of a site currently being considered for underground nuclear storage in northern Switzerland, Zürich Nordost. The results show that when a fracture is present in the vicinity of waste repository, the state parameter controlling flow through the fracture, referred to herein as fracture transmissivity, is among the important parameters which should be considered in sensitivity analysis studies.

Transient magnetohydrodynamic flow and heat transfer of fractional Oldroyd-B fluids in a microchannel with slip boundary condition

The unsteady magnetohydrodynamic flow of viscoelastic fluids through a parallel plate microchannel under the combined influence of magnetic, electro-osmotic, and pressure gradient forcings is investigated. The fractional Oldroyd-B fluid is used for the constitutive equation to simulate the viscoelastic behavior of fluid in the microchannel. Considering the important role of slip boundary condition in microfluidics, the Navier slip model at wall is adopted. The Laplace and Fourier cosine transforms are performed to derive the analytical expression of velocity distribution. Then, by employing the finite difference method, the numerical solution of the velocity distribution is given. In order to verify the validity of our numerical approach, numerical solutions and analytical solutions of the velocity distribution are contrasted with the exact solutions of the Newtonian fluid in previous work, and the agreements are excellent. Furthermore, based on the values of the velocity distribution for the fully developed flow, the energy equation including volumetric Joule heating, electromagnetic couple effect, and energy dissipation is solved to give the temperature distribution in the microchannel by using the finite difference method. Finally, the influence of fractional parameters and pertinent system parameters on the fluid flow and heat transfer performance and the dependence of the dimensionless Nusselt number Nu on the Hartmann number Ha and Brinkman number Br are discussed graphically.

Review of Steady-State Two-Phase Flow in Porous Media: Independent Variables, Universal Energy Efficiency Map, Critical Flow Conditions, Effective Characterization of Flow and Pore Network

In many applications of two-phase flow in porous media, a wetting phase is used to displace through a network of pore conduits as much as possible of a non-wetting phase, residing in situ. The energy efficiency of this physical process may be assessed by the ratio of the flow rate of the non-wetting phase over the total mechanical power externally provided and irreversibly dissipated within the process. Fractional flow analysis, extensive simulations implementing the DeProF mechanistic model, as well as a recent retrospective examination of laboratory studies have revealed universal systematic trends of the energy efficiency in terms of the actual independent variables of the process, namely the capillary number, Ca, and the flow rate ratio, r. These trends can be cast into an energy efficiency map over the (Ca, r) domain of independent variables. The map is universal for all types of non-wetting/wetting phase porous medium systems. It demarcates the efficiency of steady-state two-phase flow processes in terms of pertinent system parameters. The map can be used as a tool for designing more efficient processes, as well as for the normative characterization of two-phase flows, as to the predominance of capillary or viscous effects. This concept is based on the existence of a unique locus of critical flow conditions, for which the energy efficiency takes locally maximum values. The locus shape depends on the physicochemical characteristics of the non-wetting phase/wetting phase/porous medium system, and it shows a significant mutation as the externally imposed flow conditions change the type of flow, from capillary- to viscosity-dominated. The locus can be approached by an S-type functional form in terms of the capillary number and the system properties (viscosity ratio, wettability, pore network geometry, etc.), suggesting that formative criteria can be derived for flow characterization in any system. A new, extended definition of the capillary number is also proposed that effectively takes into account the critical properties of all the system constituents. When loci of critical flow conditions pertaining to processes with different viscosity ratio in the same pore network, are expressed in terms of this true-to-mechanism capillary number, they collapse into a unique locus. In this context, a new methodology for the effective characterization of pore networks is proposed.

Magnetohydrodynamic electroosmotic flow of Maxwell fluids with Caputo–Fabrizio derivatives through circular tubes

Unsteady flows of an incompressible Maxwell fluid with Caputo–Fabrizio time-fractional derivatives through a circular tube are studied. Flows are generated by an axial oscillating pressure gradient. The influence of a magnetic field, perpendicular on the flow direction, and of an axial electric field are considered. Solutions for the velocity and temperature fields are obtained by combining the Laplace transform with respect to the time variable t, and the finite Hankel transform with respect to the radial variable r. Influences of the order of Caputo–Fabrizio fractional time-derivative and the pertinent system parameters on the fluid flow and heat transfer performance were analyzed numerically by using the Mathcad software. Results show that the fluid velocity and the associated heat transfer modeled by fractional derivatives are quite distinct from those of the ordinary fluids. The fluid velocity and the thermal performance in cylindrical tubes can be controlled by regulating the fractional derivative parameter.

MHD natural convection flow past an impulsively started infinite vertical porous plate with Newtonian heating in the presence of radiation

Purpose– The purpose of this paper is to investigate the effects of thermal radiation and viscous dissipation on steady natural convection flow of a viscous incompressible fluid along a uniformly moving infinite vertical porous plate with Newtonian heating in the presence of transverse magnetic field. The governing non-linear boundary layer equations are solved by using homotopy analysis method (HAM). The effects of various system parameters on velocity and temperature fields are discussed graphically, and the numerical values for skin friction and Nusselt number are presented in tabular form.Design/methodology/approach– The problem is formulated using the Boussinesq approximation under the effects of thermal radiation and transverse magnetic field. The resulting coupled system of non-linear differential equations is solved using HAM with appropriate boundary conditions for Newtonian heating of the plate. HAM is a powerful method which provides rapidly converging series solution for the velocity and temperature fields. The effects of Prandtl number, Grashof number, suction parameter, magnetic field parameter, radiation parameter and Eckert number on the fluid velocity, temperature, skin friction and Nusselt number have been investigated.Findings– The HAM solution has been successfully applied to find the converging series solution for velocity and temperature fields in terms of pertinent system parameters. Comparison of the exact solution results agree well with the HAM solution results in the absence of Eckert number and this indicates that the HAM solutions are accurate. It is found that the velocity and temperature profiles decreases with the increase of thermal radiation and suction parameters. An increase in the magnetic field parameter leads to a rise in the fluid temperature and fall in the fluid velocity.Research limitations/implications– The present analysis is limited to steady state laminar natural convection flow only. Unsteady natural- /mixed-convection laminar flow in the presence of thermal radiation, chemical reaction and transverse magnetic field will be investigated in a future work.Practical implications– The study provides very useful information for heat transfer engineers to understand the heat transfer rate when the moving vertical porous surface temperature is not known a prior. The present results have immediate relevance in the design of nuclear reactors where vertical moving porous plates are using as control rods.Originality/value– The present research work is relatively original and illustrates the effects of thermal radiation, viscous dissipation and transverse magnetic field on natural convection flow past a uniformly moving infinite vertical porous plate with Newtonian heating.

Multi-state vibronic interactions in the 1,2,3-trifluorobenzene radical cation

The multi-state and multi-mode vibronic interactions between the five lowest electronic states of the title compound are investigated theoretically by an ab initio quantum dynamical approach. The well-established linear vibronic coupling scheme is adopted, augmented by quadratic coupling terms for the totally symmetric modes. The pertinent system parameters are obtained from outer valence Greens function and equation-of-motion coupled-cluster ab initio calculations. Large-scale quantum dynamical simulations are performed employing a powerful wavepacket propagation scheme. The band shapes and line structures (as far as available) of the experimental photoelectron spectra are well reproduced. Time-dependent electronic populations reveal ultrafast internal conversion processes and allow for important insight into the fluorescence properties of the radical cation. The relation to other fluoro derivatives of the benzene radical cation is discussed.

Seismic response of base-isolated buildings including soil–structure interaction

This study investigates the effect of soil–structure interaction (SSI) on the response of base-isolated buildings. The equations of motion are formulated in the frequency domain, assuming frequency-independent soil stiffness and damping constants. An equivalent fixed-base system is developed that accounts for soil compliance and damping characteristics of the base-isolated building. Closed-form expressions are derived, followed by a thorough parametric study involving the pertinent system parameters. For preliminary design, the methodology can serve as a means to assess effective use of base isolation on building structures accounting for SSI. This study concludes that the effects of SSI are more pronounced on the modal properties of the system, especially for the case of squat and stiff base-isolated structures.

Augmentation of peristaltic microflows through electro-osmotic mechanisms

The present work aims to theoretically establish that the employment of an axial electric field can substantially augment the rate of microfluidic transport occurring in peristaltic microtubes. For theoretical analysis, shape evolution of the tube is taken to be arbitrary, except for the fact that the characteristic wavelength is assumed to be significantly greater than the average radius of cross section. First, expressions for the velocity profile within the tube are derived and are subsequently utilized to obtain variations in the net flow rate across the same, as a function of the pertinent system parameters. Subsequently, the modes of interaction between the electro-osmotic and peristaltic mechanisms are established through the variations in the time-averaged flow rates for zero pressure rise and the pressure rise for zero time-averaged flow rates, as expressed in terms of the occlusion number, characteristic electro-osmotic velocity and the peristaltic wave speed. From the simulation predictions, it is suggested that a judicious combination of peristalsis and an axial electrokinetic body force can drastically enhance the time-averaged flow rate, provided that the occlusion number is relatively small.

Fault diagnostics using sliding mode techniques

This paper describes the application of sliding mode observation techniques to the problem of fault diagnostics. A specific diesel engine coolant system is considered. A non-linear sliding mode observer is used to monitor the system states. Pertinent system parameters are also monitored using the concept of the equivalent injection signal required to maintain a sliding mode. The parameter estimates from the sliding mode scheme are compared with those generated by a non-linear simulation model and are found to provide good correlation. Results from a laboratory-based power generator set (Genset) are presented to demonstrate the effectiveness of the approach.

Recent Advances In The Analysis And Interpretation Of C-O-H-N Fluids By Application Of Laser Raman Microspectroscopy

One of the major goals of a geologist is to infer, from his field and laboratory observations, the temperature, pressure, and compositional parameters of the ambient system during rock formation or ore deposition. Because fluids are actively involved in many rock-forming processes, fluid inclusions trapped within minerals are studied as evidence of the pertinent system parameters. Individual minerals may contain several generations of fluid inclusions due to the complex histories of many geological environments. Micro-analytical techniques for the measurement of small quantities of materials in individual inclusions on the order of a few micrometers in diameter therefore are required.The classical technique is microthermometry, which involves monitoring phase changes in an inclusion during controlled cooling and heating on a microscope stage. Given appropriate phase diagrams (not available in many cases) for the chemical system under study, the phase changes at recorded temperatures can be interpreted in terms of a specific fluid composition and density.

On the formation and shedding of vortices from side-wall mounted obstacles in rotating systems

The flow of a homogenous, incompressible, rotating (vertically upward) fluid past cylinders of triangular and semi-circular cross-section mounted on either the left or right wall (facing downstream) of a channel is investigated experimentally. The pertinent system parameters are the Rossby and Ekman (or Reynolds) numbers and the obstacle width to fluid depth ratio. The experiments indicate that the shedding of tip eddies from the triangular obstacle leads to a rather complex wake motion which is critically dependent on the system parameters. For certain parameter combinations the tip eddies advect downstream as single entities while in other regions of parameter space two or more eddies merge and advect downstream as large-scale eddy structures. The Strouhal numbers for both the shedding of the tip eddies as well as of the large-scale structures are measured as functions of the system parameters. Measurements of the dimensionless size of the large-scale starting eddies are made as functions of a dimensionless time and other system parameters. It is shown that eddies formed in the lee of obstacles mounted on the right (anticyclonic) tend to shed more quickly, other parameters being fixed, than those on the left (cyclonic). Measurements of the dimensionless vorticity of the cores of the large-scale structures at a fixed dimensionless time indicate that, within the accuracy of the experiments and for the range of parameters considered, this quantity is independent of the Rossby and Reynolds numbers and the side to which the obstacle is mounted. Finally some of the experimental flow patterns are shown to be similar to a recent observation of a southeastward ocean current past the western tip of Grand Bahama Island.

Traffic model and performance analysis for cellular mobile radio telephone systems with prioritized and nonprioritized handoff procedures

A traffic model and analysis for cellular mobile radio telephone systems with handoff are described. Three schemes for call traffic handling are considered. One is nonprioritized and two are priority oriented. Fixed channel assignment is considered. In the nonprioritized scheme the base stations make no distinction between new call attempts and handoff attempts. Attempts which find all channels occupied are cleared. In the first priority scheme considered, a fixed number of channels in each cell are reserved exclusively for handoff calls. The second priority scheme employs a similar channel assignment strategy, but, additionally, the queueing of handoff attempts is allowed. Appropriate analytical models and criteria are developed and used to derive performance characteristics. These show, for example, blocking probability, forced termination probability, and fraction of new calls not completed, as functions of pertinent system parameters. General formulas are given and specific numerical results for nominal system parameters are presented.

Theory of conduction in polysilicon: Drift-diffusion approach in crystalline-amorphous-crystalline semiconductor system—Part II: General I-V theory

A general model for conduction in polysilicon is presented for arbitrary applied voltage. The model incorporates the effect of mobile carrier redistribution under bias and accounts for the high field switching in amorphous grain boundary. Microscopic mobilities used for describing the carrier transport provides a physical basis for introducing the grain voltage across the unit cell of polysilicon. The voltage, in turn, distributes itself to preserve a constant current density therein. This new criterion yields a new voltage partitioning scheme, and a general expression for the corresponding current is derived in terms of pertinent system parameters.

The Covariance of Near End Crosstalk and Its Application to PCM System Engineering in Multipair Cable

The near end crosstalk (NEXT) model proposed by Cravis and Crater [1] is analyzed to give the covariance of NEXT, with good agreement between theory and measurements on multipair cable. The covariance of NEXT is then used to estimate the variance of the meansquare NEXT interference between PCM systems operating under the same cable sheath. These results are used to derive the required minimum mean NEXT loss <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\mu_{0}'</tex> as a function of the number of PCM systems <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> , the NEXT loss standard deviation σ, and pertinent PCM system parameters. Comparisons with the minimum mean NEXT loss proposed in [4] and [5], <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\mu_{0}''</tex> , and that proposed in [1], <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\mu_{0}'''</tex> , show that: <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-0.4 &lt; \mu_{0}'' - \mu_{0}' &lt; 2</tex> dB, for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1 \leq N \leq 500</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6 \leq \sigma \leq 14</tex> , while <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16 &lt; \mu_{0}''' - \mu_{0}' &lt; 6</tex> dB, for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">25 \leq N \leq 500</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6 \leq \sigma \leq 14</tex> , for all pertinent PCM system parameters.

On the Analogy Between the Calorimeter Problem and Some Granulate-Fluid Exchange Processes

The solution to a generalized version of the classical calorimeter problem approximates the behavior of certain continuous exchange processes between particulate solids and a fluid. For modeling purposes, the much simpler energy-balance solution has obvious advantages, although it only holds for negligible intraparticle resistance and thus predicts too short contact times. An error diagram provides a quantitative comparison between those two results as a function of the two pertinent system parameters.

Simple analysis and working equations for the solidification of cylinders and spheres

The analysis of solidification processes is complicated by a nonlinear boundary condition at the moving solid-liquid interface, and exact solutions are rare. Various attempts to predict the rate of solidification are available in the literature but most of the results seem to be of limited use for operation and design studies on metallurgical processes. In this article we present a physical model which can be solved analytically for the most commonly encountered boundary conditions; that is constant temperature at the cooling wall or finite heat transfer to the cooling fluid. The model is based on the assumption of a linear temperature profile in the solidified shell and a corresponding differential removal of internal energy. As a result one obtains a very simple expression for the soli-dification time as a function of the space variable and the pertinent system parameters. By comparison with numerical results the prediction error is shown to be less than 10 pet over a wide range of parameter combinations. In extreme situations, where a larger error may occur, equally accurate working equations can be generated by slightly modifying the basic results.

Carrier Acquisition for Coherent Demodulation of Pulse-Amplitude Modulation

Phase recovery in vestigial sideband (VSB) data transmission is discussed. Examining a particular aspect of this broad area, attention is focused on the time required to recover carrier phase in order to achieve a satisfactory error rate. We derive the acquisition time for simple models. Our results are exhibited graphically, relating pertinent system parameters. These results indicate that while in double sideband transmission the acquisition time required to achieve a satisfactory error rate is of the order of a few symbol intervals, in VSB transmission this time grows to tens and hundreds of symbol intervals.

Rate Optimization for Digital Frequency Modulation

The data rate of a multilevel digital FM system is optimized subject to fixed RF bandwidth, signal-to-noise ratio, and output error rate. The possibility of optimizing such a system was first considered by J. R. Pierce at Bell Telephone Laboratories. He made the observation that it is possible to send many levels slowly or fewer levels rapidly for an FM wave of fixed RF bandwidth and error rate, and that there must be a choice of signaling rate and number of levels that optimize the data rate. The rigorous treatment of this problem is the subject of this paper. The mathematical model we analyze uses frequency-shift keying at the transmitter and ideal discrimination detection with an integrate-and-dump circuit as the post-detection filter. Our results are exhibited graphically showing the various dependencies among the pertinent system parameters.

Performance of Optimum and Suboptimum Synchronizers

The optimum (maximum-likelihood) synchronizer for extracting bit synchronization directly from a binary data stream is presented along with some simple suboptimum synchronizers that perform almost as well. The manner in which the performances of these systems depend on the pertinent system parameters as determined by a combined program of analysis, simulation, and laboratory experimentation are reported. Both synchronizer jitter and the degradation in error rate due to jitter are considered.

Average Control for Sinusoidal- and Random-Vibration Testing

Time-division multiplexers (TDM) have found application in providing control from the average of several acceleration magnitudes for swept-sinusoidal vibration tests and, also, control to the average of several acceleration spectral densities for wide-band random tests. The vibration testing systems using the TDM are described. Pertinent system parameters are determined mathematically in order to limit signal harmonic distortion for the sinusoidal case, and to limit test-level modulation and spectral spreading for the random case. A special case for sinusoidal testing in which a narrow-band tracking filter is used on the output of the TDM is also discussed.