New Set Of Equations Research Articles

Apnea bradycardia detection based on new coupled hidden semi Markov model.

In this paper, a method for apnea bradycardia detection in preterm infants is presented based on coupled hidden semi Markov model (CHSMM). CHSMM is a generalization of hidden Markov models (HMM) used for modeling mutual interactions among different observations of a stochastic process through using finite number of hidden states with corresponding resting time. We introduce a new set of equations for CHSMM to be integrated in a detection algorithm. The detection algorithm was evaluated on a simulated data to detect a specific dynamic and on a clinical dataset of electrocardiogram signals collected from preterm infants for early detection of apnea bradycardia episodes. For simulated data, the proposed algorithm was able to detect the desired dynamic with sensitivity of 96.67% and specificity of 98.98%. Furthermore, the method detected the apnea bradycardia episodes with 94.87% sensitivity and 96.52% specificity with mean time delay of 0.73 s. The results show that the algorithm based on CHSMM is a robust tool for monitoring of preterm infants in detecting apnea bradycardia episodes. Graphical Abstract Apnea Bradycardia detection using Coupled hidden semi Markov Model from electrocardiography. In this model, a sequence of hidden states is assigned to each observation based on the effects of previous states of all observations.

Heat transfer modeling of non-boiling gas-liquid slug flow using a slug tracking approach

This study proposes a new set of equations for the energy balance for predicting the temperature distribution of gas-liquid slug flows using a slug tracking approach. The model proves able to work around non-physical oscillations of the temperature distribution found with a previously published set of equations for the energy balance. The main difference here is that rather than being applied to each structure (namely the liquid slug, the liquid film and the elongated bubble) individually, the temperature is assigned to the whole unit cell. Central Differencing Schemes were avoided since the problem is convection-dominant, thus preference to Upwind Differencing Schemes was given. Comparison of the new model with an experimental dataset for air-water flow in a 52-mm ID pipeline showed deviations of ±25% for the temperature and pressure gradients. An extra head loss term caused by the recirculation of liquid in the elongated bubble wake was introduced into the momentum balance, correcting an existing –20% systematic deviation found in the pressure gradient as computed by the former model. Simulations for an extended, 200-m long pipeline comparing isothermal, cooling and heating flows are also presented. These simulations demonstrate the competition of gas expansion caused by pressure drop and of gas expansion/contraction caused by mixture heating/cooling, and their consequences on the elongated bubble length increase/decrease, on the mixture acceleration/deceleration, on the coalescence rate of elongated bubbles, and on their statistic distributions.

Interaction of micropolar fluid structure with the porous media in the flow due to a rotating cone

A model of heat and mass transfer of two dimensional MHD micropolar fluid over a cone is constructed. Similarity transformation is adopted for the conversion of partial differential equations into ordinary differential equations have been linearized by employing the Newton’s linearization technique and then new sets of equations are discretized using the finite difference method. The impact of non-dimensional parameters is further analyzed and the numerical results for profiles of velocity, temperature and concentration are expressed graphically and the results are discussed in detail. For the higher values of Dufour number, temperature field is enhanced graphically but show the opposite behavior in case of Prandlt number. Furthermore, the micro-rotation parameter show decreasing behavior with the enhancing of magnetic and porosity parameters respectively.

On (non-)dynamical dark energy

The current Universe is composed by a mixture of relativistic species, baryonic matter, dark matter and dark energy which evolve in a non-trivial way at perturbative level. An advanced description of the cosmological dynamics should include non-standard features beyond the simplistic approach idealized by the standard cosmology in which cosmic components do not interact, are adiabatic and dissipationless. We promote a full perturbative analysis of linear scalar perturbations of a non-interacting cosmological model containing baryons, dark matter (both pressureless) and a scalar field allowing for the presence of relative entropic perturbations between the three fluids. Assuming an effective scalar-field sound speed equal to one and neglecting anisotropic stresses we establish a new set of equations for the scalar cosmological perturbations. As a consequence of this new approach, we show that tiny departures from a constant scalar field equation of state $w_S=-1$ damage structure formation in a non-acceptable manner. Hence, by strongly constraining $w_S$ our results provide compelling evidence in favor of the standard cosmological model and rule out a large class of dynamical dark energy models

A composite microstructural and geochemical approach to quench the quest for hydrocarbon from Barren Measures shales of Jharia Basin, India

The present study portraits the organic petrological, geochemical and microstructural characters of twenty borehole shale samples for assessing the hydrocarbon generation proficiency of the shales from the Barren Measures Formation (a stratigraphic unit of the Gondwana that is devoid of any workable coal seam) of the Jharia Basin, India, which was underinvestigated until now. The samples consist of vitrinite grains ranging from 5.41 to 20.57 vol%, the dominance of which compared to the inertinite and liptinites may reflect the lignocellulosic organic matter (type-III kerogen) input from the terrestrial plants. The range of the mean random vitrinite reflectance values (0.93–1.27%) may suggest the gas generation potential of the shale samples. The peak palaeotemperature values, may, in addition, suggest wet gas generation from these shales in complementary to some shale samples having efficiency to generate dry gas. The total organic carbon in these samples ranging between 3.87 and 15.99 wt% may imply good to excellent hydrocarbon generation capability. Rock Eval pyrolysis suggests the input of type-III kerogen within the mire and the correlations of the pyrolysis parameters exhibit that the shale samples possess significant potential to generate gaseous hydrocarbons (shale gas). The factor of kerogen conversion (f) of many shales suggests almost 20–30% transformation of kerogen to hydrocarbons. On attaining sufficient thermal maturity, the remaining large amount of labile chemical moieties may convert to hydrocarbons. The positive relation of the present-day hydrogen index (HIpd) with the A-factor would suggest the depletion of hydrogen containing functional groups for generating the gaseous hydrocarbons (shale gas). The Raman spectra of the samples reveal poorly organized microstructure, possibly, due to the presence of labile aliphatic compounds that would yet to generate hydrocarbons on attaining relevant thermal maturity as well as because of partially condensed aromatic system containing heteroatoms. The correlations of the Raman data with the mean random vitrinite reflectance data reveal generation of wet and dry gas from these shale samples based on the maturity level. The scientific content of this present study lies in suggesting a set of new equations from the relations obtained between of the Raman spectral parameters and the Rock Eval data in order to suggest the applicability of the Raman spectroscopy in elucidating the shale gas potential. These may be considered as the addendum to the applications of the existing techniques to elucidate the hydrocarbon potential of the organic-rich source rocks, which also add the novelty of this investigation. The new equations and the relations may be tested in the samples of different thermal maturity from other basins for substantiating their world-wide applications.

Head Losses of Horizontal Bar Racks as Fish Guidance Structures

Horizontal bar racks have been used as trash racks at hydropower plants since the 1920s. With the installation of the first horizontal bar rack bypass system at a hydropower plant as a downstream fish passage facility in 2006, these racks rapidly gained importance as fish protection measures. Since then, they have been installed at more than 100 small- to medium-sized hydropower plants in Europe. Despite the large number of installed racks, systematic investigations of the head losses and velocity fields were missing. On the basis of detailed hydraulic experimentation with a large number of rack parameters and including up-to-date foil-shaped bars, the layout of horizontal bar racks and their hydraulic performance were assessed in the current study. This paper reports the results of the rack head loss investigation, whereas the accompanying paper entitled Velocity Fields at Horizontal Bar Racks as Fish Guidance Structures focuses on the up- and downstream velocity fields. By applying foil-shaped bars instead of rectangular bars, the loss coefficient was reduced by more than 40%, depending on the rack configuration. Bottom and top overlays are used to increase the guidance efficiency for fish, sediments, and floating debris. However, the altered flow field results in increased head losses. A new set of equations is proposed to predict head losses for current horizontal bar racks, including overlays for various hydropower plant layouts. The predictions are compared to literature data.

New Predictive Equations for Resting Energy Expenditure in Normal to Overweight and Obese Population.

Background and Aims The unique demographic and dietary characteristics of modern Arabic population require development of a new predictive equation for the estimation of resting energy expenditure (REE). This study presented new equations characteristic to Saudi population. Methods A set of predictive equations for REE was derived for 427 healthy male and female subjects (aged 18–57 ± 14 years). REE was measured (REEm) by indirect calorimetry (IC) and predicted (REEp) using nine equations. REEp was compared with REEm to determine the predictive accuracy of these equations. Using IC and anthropometrics for stepwise linear regression analysis, a new set of equations to predict REE of men and women was developed. Accuracy of the new main equations was further tested in an external sample of 48 subjects (men = 50%). Results Using a number of parameters (bias, underprediction, overprediction, and % accurate prediction), our results suggested that almost all (9/9 in men and 7/9 in women) equations either underpredicted or overpredicted (2/9) REE. None of the already existing equations showed an acceptable REEp/REEm difference as low as 5% and an accurate prediction (∼55%) at the individual level. Based on these findings, a new prediction equation (hereafter referred to as the Almajwal–Abulmeaty (AA) equation) was developed using this study's data, after a rigorous stepwise regression analysis using the following formula: REE = 3832.955 + AdjWt (kg) × 48.037 − Ht (cm) × 30.642 + gender × 141.268 − age (years) × 4.525 [AdjWt is Adjusted body weight = (Wt − IBW)/4 + IBW. IBW is Ideal body weight; for men IBW = (Ht(cm) − 152.4) × 1.0714) + 45.36 and for women IBW = (Ht(cm)−152.4) × 0.8928) + 45.36]. The regression model accounted for approximately 70% of the variance in REEm (R2 = 0.702). Conclusion Previous equations likely over- or underpredicted REE. Therefore, the new predictive AA equations developed in this study are recommended for the estimation of REE in young to middle-aged Saudi men and women with different body mass indexes. Future research is also required for further clinical and cross-validation of these new equations.

Wave Forecasting in Shallow Water: A New Set of Growth Curves Depending on Bed Roughness

Forecasting relationships have been recognized as an important tool to be applied together, or not, with complete numerical modelling in order to reconstruct the wave field in coastal areas properly when the available wave data is limited. In recent years, the literature has offered several comprehensive sets of field experiments investigating the form of the asymptotic, depth-limited wind waves. This has made it possible to reformulate the original deep water equations, taking into account the effects of water depth, if wind waves are locally generated in shallow and confined basins. The present paper is an initial attempt to further contribute to the shallow water forecasting curves which are currently available, also considering the role on the wave generation of a variable equivalent bottom roughness. This can offer the possibility of applying shallow growth curves to a broad variety of contexts, for which bed composition and forms can be different. Simple numerical tests have been conducted to reproduce the fully developed conditions of wave motion with variable roughness values. To validate the new set of equations, they have been applied to a real shallow lake for which both experimental and numerical wave data is available. The comparison of the obtained results is very encouraging in proceeding with this approach.

Design of high-performance double quantum well vertical cavity transistor lasers with GRIN base region

Different confinement structures are analyzed to achieve higher optoelectronic performances for double quantum well vertical cavity transistor laser with graded index separate confinement heterostructure. Adding the drift component to the diffusion term of the current density and solving new sets of equations, modified electro-optic performances of the device is obtained. Band-gap engineering of the original structure predicts simultaneous improvements in both current gain (more than two times) and −3 dB optical bandwidth (by 1.5 GHz). Other less critical, yet important, performance metrics including optical output power and threshold current (up to 20%) are enhanced due to applying graded layers of AlξGa1-ξAs in the base region.

Modelling mechanical percolation in graphene-reinforced elastomer nanocomposites

Graphene is considered an ideal filler for the production of multifunctional nanocomposites; as a result, considerable efforts have been focused on the evaluation and modelling of its reinforcement characteristics. In this work, we modelled successfully the mechanical percolation phenomenon, observed on a thermoplastic elastomer (TPE) reinforced by graphene nanoplatelets (GNPs), by designing a new set of equations for filler contents below and above the percolation threshold volume fraction (Vp). The proposed micromechanical model is based on a combination of the well-established shear-lag theory and the rule-of-mixtures and was introduced to analyse the different stages and mechanisms of mechanical reinforcement. It was found that when the GNPs content is below Vp, reinforcement originates from the inherent ability of individual GNPs flakes to transfer stress efficiently. Furthermore, at higher filler contents and above Vp, the nanocomposite materials displayed accelerated stiffening due to the reduction of the distance between adjacent flakes. The model derived herein, was consistent with the experimental data and the reasons why the superlative properties of graphene cannot be fully utilized in this type of composites, were discussed in depth.

Application of an augmented Lagrangian approach to multibody systems with equality motion constraints

The focus of this work is on dynamics of multibody systems subject to bilateral motion constraints. First, a new set of equations of motion is employed, expressed as a coupled system of strongly nonlinear second-order ordinary differential equations. After putting these equations in a weak form, the position, velocity and momentum type quantities are assumed to be independent. This leads to a three-field set of equations of motion. Next, an alternative formulation is developed, based on optimization principles. It is shown that the equations of motion can eventually be cast in a form obtained by application of an augmented Lagrangian formulation, after introducing an appropriate set of penalty terms. This final set of equations is then used as a basis for developing a new time integration scheme. The validity and numerical efficiency of this scheme is verified by applying it to several example systems. In those examples, special emphasis is put on illustrating the advantages of the new method when applied to selected mechanical systems, involving redundant constraints or singular configurations.

New Analytical Model Enhances Understanding of Connection Strengths

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 194180, “An Analytical Model for Double-Shouldered Connection Strengths,” by Grant Pettit, SPE, Bureau Veritas, prepared for the 2019 SPE/IADC International Drilling Conference and Exhibition, The Hague, 5–7 March. The paper has not been peer reviewed. The extra torsional capacity and clearance available when proprietary, double-shouldered connections are used instead of public-domain, single-shouldered connections enables well teams to drill farther, faster, and with less damage to the drillstring. No analytical model as yet can accurately calculate the tensile and torsional capacities of double-shouldered connections. This paper presents a set of equations that extends the approach of the original single-shouldered equation to account for a second shoulder, and helps to understand connection strengths better. Introduction Single-shouldered connections such as API drillstem connections use a straightforward analytical equation to determine the capacities of any connection. This equation may not be perfect—it relies on linear assumptions that are probably not descriptive of the connection loading—but several decades of use have made the industry confident in the equation’s strengths and aware of its shortcomings. Because no analytical model is available to calculate these capacities in proprietary double-shouldered connections, the connection designer or manufacturer typically creates an empirical formula that is calibrated through laboratory and field testing. Although this approach is acceptable, it hinders tool designers who need something different from what is offered on the public market. It is rarely cost-efficient to perform laboratory and field testing for a one-off connection design. The complete paper states that what is needed is to extend the approach of the original single-shouldered equation to account for a second shoulder. According to the author, although the mathematical complexity increases, the assumptions are the same, lending confidence to the extended equation. The complete paper presents the derivation of a set of equations that use the same basic assumptions as the original single-shouldered connection torque equations, in the same way as do the API equations, to advance understanding of the torsion and tension capacities for double-shouldered equations. The implicit assumptions present in the original equations are discussed; then the same ideas are applied to a double-shouldered connection. The full set of new equations is developed and described, including tips on their practical use gained from tool-design experience. Current Single-Shouldered Connection Model Connection strength formulas contained in API RP 7G Appendix A are the basis for the connection torsion and tensile capacities in that standard and in many other oilfield references. These equations and resulting numbers have been in place for decades, creating industry confidence in their usefulness and awareness of their weaknesses.

A Nonlocal Theory of Current-Driven Low-Frequency Modes in a Magnetized Strongly Coupled Collisional Dusty Plasma

The nonlocal theoretical model developed to observe current-driven low-frequency electrostatic modes in a collisional magnetized strongly coupled dusty plasma, in the strongly coupled kinetic regime ωτ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ≫ 1 (i.e., wave frequency is much larger than the dust particle relaxation time) led to a new set of equations for dispersion relation, frequency, and the growth rate. The theoretical investigations on a cylindrical magnetized strongly coupled dusty plasma led to a current driven ion dust hybrid like longitudinal dust wave propagating nearly along radial direction and a peculiar transverse shear dust wave mode along axial direction. Dispersion properties of both longitudinal dust acoustic modes and transverse shear modes are modified in the presence of ion and dust currents and the effective perpendicular wave number provided by finite geometry of strongly coupled magnetized dusty plasma. The magnetic field has a destabilizing effect on the growth of longitudinal wave modes, while the dependence of transverse modes on the strength of magnetic field is not prominent. Transverse shear modes are characterized as the short wavelength modes with a long wavelength cutoffs. A comparison of nonlocal effects with local effects shows that in bounded magnetized strongly coupled dusty plasmas, the longitudinal wave modes need a large magnetic field and weak collisional regime to support the excitation of dust wave modes, whereas the transverse modes are a consequence of viscous and collisional damping.

Automatic schemes for including generator Q and transformer tap limits in the fast decoupled load flow method

This study proposes a modified formulation for the popular fast decoupled load flow method to facilitate automatic incorporation of reactive power flow related constraints, i.e. generator reactive power and in-phase transformer tap limits. This formulation has been developed by viewing each device constraint as a set of complementary conditions and adopting the complementarity framework to define one equation to represent this set. The original set of load flow equations is augmented with this set of new equations representing the device constraints and solved to get the adjusted solutions directly. This approach is a significant departure from all the earlier approaches. The earlier approaches generally adopt a two-stage scheme. In the first stage, an approximate unadjusted solution is obtained and in the next stage, adjustments are attempted by ad hoc schemes. The new formulation presented here permits handling both the reactive power related constraints simultaneously. However, it can also be used in situations where only one type of adjustment is needed. Two alternate algorithms in complementarity framework based on mixed complementarity problem and non-linear complementarity problem formulations are presented here. Simulation results are presented to provide evidence of the impressive performance of the new algorithms as compared with the existing ones.

Hadronic Matter in the Robertson–Walker Metric and the Early Universe

In this work, the equations for hadronic matter in the Robertson–Walker metric in the early Universe are obtained. We consider the hadronic phase, formed after the hadronization of the quark-gluon plasma, that means times from 10–6 to 1 s. A new set of equations, determined by fields in a curved space-time, is derived, and the behavior of this system is studied.

Multiparticle time-domain analysis of coherent undulator radiation

The physics involving the emission of coherent undulator radiation from a bunch of correlated electrons wiggling inside an undulator has been very well established in the frequency domain. With the aim of describing the process of emission of coherent undulator radiation in time domain while incorporating the effect of hyperbolic field profile of the undulator and various electron beam parameters, we present a time-domain analysis which can serve as a complimentary formulation to the frequency-domain analysis of the coherent undulator radiation. The formulation requires revisiting the equation of motion of an electron moving inside a planar undulator. An electron beam with substantial spread along the direction of the magnetic field will undergo betatron oscillations due to the hyperbolic profile of the undulator fields. We show that the betatron motion can be conveniently expressed in terms of Mathieu functions. The new set of equations of motion have been used to study the effect of betatron motion on the emitted undulator radiation. The single-particle time-domain analysis is then easily extended to multiparticle systems by correctly accounting for the phase-difference between the individual electromagnetic waves emitted by different electrons occupying different phase-space in the bunch.

A consistent approach to particle shifting in the [formula omitted]-[formula omitted]-SPH model

In the present work a consistent inclusion of a particle shifting technique (PST) in the weakly compressible Smoothed Particle Hydrodynamic (SPH) models is discussed. Recently, it has been shown that the use of PST can largely improve both the accuracy and the robustness of SPH models. In particular, the δ+-SPH model is a weakly-compressible SPH model where a PST is adopted along with a diffusive term in the continuity equation that helps removing the high-frequency noise on the pressure field. This specific SPH model is able to overcome the main drawbacks that afflict the standard weakly-compressible SPH model. In this work we demonstrate that a consistent introduction of the PST inside the SPH model leads to a new set of equations where some additional terms containing the particle shifting velocity δu have to be taken into account. The effects of these δu-terms become crucial for problems in confined or periodic domains, as well as for long-time simulations of free-surface flows. The proposed scheme is tested against challenging benchmark cases, highlighting when the δu-terms play an important role or not. Further improvements of the PST algorithms for the numerical treatment of the scheme close to the free surface and along the solid boundaries are also discussed.

Numerical investigation of pressure and flow characteristics of pleated air filter system for automotive engine intake application

This article presents a numerical methodology for estimation of flow field and pressure drop within a pleated air filter system that is typically used for automotive engine intake application. The flow field within the air filter housing was found to be highly non-uniform. This flow field was utilized to simulate the pressure drop across a typical pleated air filter element. Both the flow field and pressure drop were experimentally determined and they were found to be in good agreement with the simulation results. A set of new equations for pleat angle and maximum possible pleat radius was proposed to parameterize the pleat geometry. An optimal pleat pitch was determined to obtain minimum pressure drop and this was found to be dependent on pleat height significantly. The effect of pleat radius on the pressure drop was examined at optimum pleat pitch and pleat height. The pleat geometry and inlet velocity were found to be the key determinants of evolution of flow velocity within the pleated filter element and also at the vicinity of the filter media.

Assessment of embankment dams breaching using large scale physical modeling and statistical methods

Understanding the failure mechanisms of embankment dams due to overtopping is essential for the design of flood mitigation, flood mapping, and flood warning systems. The breach process in embankment dams can be characterized using breach parameters such as breach opening dimensions, time of breach formation, and peak breach outflow. The main objective of this study is to derive new set of statistical equations to predict the target breach parameters. A database of 126 events of embankment failure was collected and then multiple nonlinear regression analysis is used to derive the new set of equations and the uncertainty in the computed parameters was quantified. Finally, five large-scale overtopping failure tests were conducted on cohesive and non-cohesive soils embankments. The derived breach parameters equations showed good agreement with the results of the physical models for non-cohesive soil embankments, while the failure of cohesive soil embankments varied significantly with soil properties; indicating that breach parameters in cohesive soil embankment should be computed based on not only embankment dimensions but soil properties as well.

Adiabatic approach to large-amplitude collective motion with the higher-order collective-coordinate operator

We propose a new set of equations to determine the collective Hamiltonian including the second-order collective-coordinate operator on the basis of the adiabatic self-consistent collective-coordinate (ASCC) theory. We illustrate, with the two-level Lipkin model, that the collective operators including the second-order one are self-consistently determined. We compare the results of the calculations with and without the second-order operator and show that, without the second-order operator, the agreement with the exact solution becomes worse as the excitation energy increases, but that, with the second-order operator included, the exact solution is well reproduced even for highly excited states. We also reconsider which equations one should adopt as the basic equations in the case where only the first-order operator is taken into account, and suggest an alternative set of fundamental equations instead of the conventional ASCC equations. Moreover, we briefly discuss the gauge symmetry of the new basic equations we propose in this paper.