Vacuum Model Research Articles

Cortex Effect on Vacuum Drying Process of Porous Medium

Corns, fruits, and vegetables are usually used as porous medium in drying process. But in fact, it must be considered as the cortex effect on mass transfer because the mass transfer of cortex is very difficult than inner medium. Based on the theory of heat and mass transfer, a coupled model for the porous medium vacuum drying process with cortex effect is constructed. The model is implemented and solved using COMSOL software. The water evaporation rate is determined using a nonequilibrium method with the rate constant parameterKrthat has been studied. The effects of different vapor pressures (1000, 5000, and 9000 Pa), initial moisture contents (0.3, 0.4, and 0.5 water saturation), drying temperatures (323, 333, and 343 K), and intrinsic permeability for cortex part (10−13, 10−14, 10−15 m2) on vacuum drying process were studied. The results facilitate a better understanding of the porous medium vacuum drying process that nearer to the reality.

Smooth Gowdy-symmetric generalized Taub–NUT solutions

We study a class of -Gowdy vacuum models with a regular past Cauchy horizon which we call smooth Gowdy-symmetric generalized Taub–NUT solutions. In particular, we prove the existence of such solutions by formulating a singular initial value problem with asymptotic data on the past Cauchy horizon. We prove that also a future Cauchy horizon exists for generic asymptotic data, and derive an explicit expression for the metric on the future Cauchy horizon in terms of the asymptotic data on the past horizon. This complements earlier results about -Gowdy models.

Octet baryon electromagnetic form factors in nuclear medium

We study the octet baryon electromagnetic form factors in nuclear matter using the covariant spectator quark model extended to the nuclear matter regime. The parameters of the model in vacuum are fixed by the study of the octet baryon electromagnetic form factors. In nuclear matter the changes in hadron properties are calculated by including the relevant hadron masses and the modification of the pion–baryon coupling constants calculated in the quark–meson coupling model. In nuclear matter the magnetic form factors of the octet baryons are enhanced in the low Q2 region, while the electric form factors show a more rapid variation with Q2. The results are compared with the modification of the bound proton electromagnetic form factors observed at Jefferson Lab. In addition, the corresponding changes for the bound neutron are predicted.

Spike oscillations

According to Belinski\ifmmode \check{i}\else \v{i}\fi{}, Khalatnikov and Lifshitz (BKL), a generic spacelike singularity is characterized by asymptotic locality: Asymptotically, toward the singularity, each spatial point evolves independently from its neighbors, in an oscillatory manner that is represented by a sequence of Bianchi type I and II vacuum models. Recent investigations support this conjecture but with a modification: Apart from local BKL behavior there also exists formation of spatial structures (``spikes'') at, and in the neighborhood of, certain spatial surfaces that break asymptotic locality; the complete description of a generic spacelike singularity involves spike oscillations, which are described by sequences of Bianchi type I and certain inhomogeneous vacuum models. In this paper we describe how BKL and spike oscillations arise from concatenations of exact solutions in a Hubble-normalized state space setting, suggesting the existence of hidden symmetries and showing that the results of BKL are part of a greater picture.

Vacuum structure and string tension in Yang-Mills dimeron ensembles

We numerically simulate ensembles of SU(2) Yang-Mills dimeron solutions with a statistical weight determined by the classical action and perform a comprehensive analysis of their properties as a function of the bare coupling. In particular, we examine the extent to which these ensembles and their classical gauge interactions capture topological and confinement properties of the Yang-Mills vacuum. This also allows us to put the classic picture of meron-induced quark confinement, with the confinement-deconfinement transition triggered by dimeron dissociation, to stringent tests. In the first part of our analysis we study spacial, topological-charge and color correlations at the level of both the dimerons and their meron constituents. At small to moderate couplings, the dependence of the interactions between the dimerons on their relative color orientations is found to generate a strong attraction (repulsion) between nearest neighbors of opposite (equal) topological charge. Hence, the emerging short- to mid-range order in the gauge-field configurations screens topological charges. With increasing coupling this order weakens rapidly, however, in part because the dimerons gradually dissociate into their less localized meron constituents. Monitoring confinement properties by evaluating Wilson-loop expectation values, we find the growing disorder due to the long-range tails of these progressively liberated merons to generate a finite and (with the coupling) increasing string tension. The short-distance behavior of the static quark-antiquark potential, on the other hand, is dominated by small, ``instantonlike'' dimerons. String tension, action density and topological susceptibility of the dimeron ensembles in the physical coupling region turn out to be of the order of standard values. Hence, the above results demonstrate without reliance on weak-coupling or low-density approximations that the dissociating dimeron component in the Yang-Mills vacuum can indeed produce a meron-populated confining phase. The density of coexisting, hardly dissociated and thus instantonlike dimerons seems to remain large enough, on the other hand, to reproduce much of the additional phenomenology successfully accounted for by nonconfining instanton vacuum models. Hence, dimeron ensembles should provide an efficient basis for a more complete description of the Yang-Mills vacuum.

Quark condensate for various heavy flavors

The quark condensate is calculated within the world-line effective-action formalism, by using for the Wilson loop an ansatz provided by the stochastic vacuum model. Starting with the relation between the quark and the gluon condensates in the heavy-quark limit, we diminish the current quark mass down to the value of the inverse vacuum correlation length, finding in this way a 64%-decrease in the absolute value of the quark condensate. In particular, we find that the conventional formula for the heavy-quark condensate cannot be applied to the c-quark, and that the corrections to this formula can reach 23% even in the case of the b-quark. We also demonstrate that, for an exponential parametrization of the two-point correlation function of gluonic field strengths, the quark condensate does not depend on the non-confining non-perturbative interactions of the stochastic background Yang-Mills fields.

Generalizing the running vacuum energy model and comparing with the entropic-force models

We generalize the previously proposed running vacuum energy model by including a term proportional to \dot{H}, in addition to the existing H^2 term. We show that the added degree of freedom is very constrained if both low redshift and high redshift data are taken into account. Best-fit models are undistinguishable from LCDM at the present time, but could be distinguished in the future with very accurate data at both low and high redshifts. We stress the formal analogy at the phenomenological level of the running vacuum models with recently proposed dark energy models based on the holographic or entropic point of view, where a combination of \dot{H} and H^2 term is also present. However those particular entropic formulations which do not have a constant term in the Friedmann equations are not viable. The presence of this term is necessary in order to allow for a transition from a decelerated to an accelerated expansion. In contrast, the running vacuum models, both the original and the generalized one introduced here contain this constant term in a more natural way. Finally, important conceptual issues common to all these models are emphasized.

Observation of Lobes near theXPoint in Resonant Magnetic Perturbation Experiments on MAST

The application of nonaxisymmetric resonant magnetic perturbations (RMPs) with a toroidal mode number n = 6 in the MAST tokamak produces a significant reduction in plasma energy loss associated with type-I edge localized modes (ELMs), the first such observation with n > 3. During the ELM mitigated stage clear lobe structures are observed in visible-light imaging of the X-point region. These lobes or manifold structures, that were predicted previously, have been observed for the first time in a range of discharges and their appearance is correlated with the effect of RMPs on the plasma; i.e., they only appear above a threshold when a density pump out is observed or when the ELM frequency is increased. They appear to be correlated with the RMPs penetrating the plasma and may be important in explaining why the ELM frequency increases. The number and location of the structures observed can be well described using vacuum modeling. Differences in radial extent and poloidal width from vacuum modeling are likely to be due to a combination of transport effects and plasma screening.

Bound states in modified action for light quarks in instanton vacuum model

Within the zero fermion mode approximation and using the instanton liquid action modified by the effective determinant interaction we are able to describe low-lying bound states in the pseudoscalar channel for the pion as well in the vector channel for the ρ-meson.

Analysis of stochastic magnetic fields formed by the application of resonant magnetic perturbations on MAST and comparison with experiment

In MAST experiments with applied resonant magnetic perturbations (RMPs), clear reduction in line-averaged density has been observed in a wide range of L-mode plasmas when there is an alignment between the perturbation and the equilibrium magnetic field that maximizes the size of the resonant components of the applied magnetic field, as well as in a few H-mode plasmas but with a much stronger sensitivity to this alignment. This density pump-out is the result of increased particle transport, which is thought to be caused by the formation of a stochastic magnetic field in the plasma edge. This paper presents an analysis of the magnetic field structures formed by the application of n = 3 RMPs on MAST, including various parameters characterizing the degree of stochasticity in the plasma edge. Values for these parameters are calculated and compared with the amount of density pump-out observed in MAST experiments. It is found that density pump-out is fairly well correlated with some of the parameters calculated using vacuum modelling, but none of them provides a single threshold value for pump-out that applies to both L- and H-mode plasmas. Plasma response modelling provides a robust criterion for density pump-out that applies both to L- and H-mode plasmas.

Vacuum-assisted vaginal delivery simulation – quantitation of subjective measures of traction and detachment forces

Objective: Excessive traction has been alleged as the cause of newborn complications associated with vacuum delivery. We sought to quantify subjective levels of physician vacuum traction in a simulated obstetric delivery model, dependent upon level of training. Methods: Three groups of physicians, based on training level applied traction (minimal, average, maximal) on a pre-applied vacuum model and forces were continually recorded. Detachment force was recorded with traction in both the pelvic axis and at an oblique angle. Results: Quantified traction force increased from subjective minimal to average to maximal pulls. Within each level, there were no differences between the groups in the average traction force. Detachment force was significantly less when traction was applied at an oblique angle as opposed to the pelvic axis (11.1 ± 0.3 vs 12.2 ± 0.3 kg). Conclusion: Providers appear to be good judges of the force being applied, as a clear escalation in force is noted with minimal, average and maximal force pulls. There appears to be a relatively short learning curve for use of the vacuum, as junior residents’ applied force was not different from those of more experienced practitioners. Using the KIWI device, detachment force is lower when traction is applied at an oblique angle.

The model of superfluid physical vacuum as a basis for explanation of efficacy of highly diluted homeopathic remedies

The results of using homeopathic remedies for treatment of milking cows with mastitis and calves with gastrointestinal disorders are described. An explanation of effects of highly diluted homeopathic remedies, based on a model of superfluid physical vacuum, is provided. Under assumption that physical vacuum has the properties of superfluid 3 Не-В, the effects of ultra-low doses can be taken due to spin supercurrents between spin structures produced in the superfluid physical vacuum by the biologically active substance and the target biological object. The properties of the spin supercurrents are similar to those in superfluid 3 He-B.

The Atomistic Revival

In our recent book (Abraham and Roy 2010) we have repurposed a mathematical model for the quantum vacuum as a model of consciousness. In this model, discrete space and time are derived from a discrete cellular dynamical network. As our model is essentially atomistic, we included in our book a short support chapter on atomism. In this aticle we expand on the few pages of that chapter devoted to the history of atomism, to place the current revival of atomism in a larger context.

Role of Anomalous Quark-Gluon Chromomagnetic Interaction in Hadron Physics

We calculate the contribution arising from nonperturbative quark-gluon chro- momagnetic interaction to the high energy total quark-quark cross section. The estimation obtained within the instanton model of QCD vacuum leads to the conclusion that this type of interaction gives the dominating contribution to the Pomeron coupling with the light quarks and to gluon distribution in light hadrons at small virtualities of quarks and gluons.

Nonequilibrium Thermal Dynamic Modeling of Porous Medium Vacuum Drying Process

Porous medium vacuum drying is a complicated heat and mass transfer process. Based on the theory of heat and mass transfer, a coupled model for the porous medium vacuum drying process is constructed. The model is implemented and solved using COMSOL software. The water evaporation rate is determined using a nonequilibrium method with the rate constant parameter Kr. Kr values of 1, 10, 1000, and 10000 are simulated. The effects of vapor pressures of 1000, 5000, and 9000 Pa; initial moistures of 0.6, 0.5, and 0.4 water saturation; heat temperatures of 323, 333, and 343 K; and intrinsic permeability of 10−13, 10−14, and 10−15 m2 are studied. The results facilitate a better understanding of the porous medium vacuum drying process.

Porous media based model for deep-fat vacuum frying potato chips

Vacuum frying is an alternative method to the traditional atmospheric deep-fat frying that offers the health benefits associated with lower concentrations of acrylamide and less adverse effects on oil quality while still preserving the natural color and flavor of the product.A multiphase porous media model involving heat and mass transfer within a potato chip was implemented in a commercial CFD program. Simulations were run at different frying pressures of 1.33kPa, 9.89kPa, 16.7kPa, and 101kPa. Good agreement between predicted and literature experimental moisture, oil, and acrylamide content was obtained. Regardless of fryer pressure, the model showed the core pressure reached approximately 40kPa higher than the surface. The model modified Darcy’s law to account for the Klinkenberg effect.

CMB temperature and matter power spectrum in a decay vacuum dark energy model

In this paper, a decay vacuum model ${\overline{\ensuremath{\rho}}}_{\ensuremath{\Lambda}}=3\ensuremath{\sigma}{M}_{p}^{2}{H}_{0}H$ is revisited by detailed analysis of background evolution and perturbation equations. We show the imprints on CMB temperature and matter power spectrum from the effective coupling terms between dark sectors by comparing to the standard cosmological constant model and observational data points (WMAP7 and SDSS DR7). We find that the decay vacuum model can describe the expansion rate at late times as well as the standard cosmological constant model but it fails to simultaneously reproduce the observed CMB and matter power spectrum. Its generalization ${\overline{\ensuremath{\rho}}}_{\ensuremath{\Lambda}}=3{M}_{p}^{2}({\ensuremath{\xi}}_{1}{H}_{0}H+{\ensuremath{\xi}}_{2}{H}^{2})$ is also discussed. Detailed analysis of the background evolution shows that the dimensionless parameter ${\ensuremath{\xi}}_{2}$ would be zero to avoid the unnatural ``fine-tuning'' and to keep the positivity of energy density of dark matter and dark energy in the early epoch.

Functionalization of, and Deposition on Complex‐Shaped Surfaces: Vacuum Processes, Materials, Models, Challenges, and Methods

Functionalization of, and Deposition on Complex‐Shaped Surfaces: Vacuum Processes, Materials, Models, Challenges, and Methods

How self-dual is QCD?

Vacuum characteristics quantifying dynamical tendency toward self-duality in gauge theories could be used to judge the relevance of classical solutions or the viability of classically motivated vacuum models. Here we decompose the field strength of equilibrium gauge configurations into self-dual and anti-self-dual parts, and apply absolute X-distribution method to the resulting polarization dynamics in order to construct such characteristics. Using lattice regularization and focusing on pure-glue SU(3) gauge theory at zero temperature, we find evidence for positive but very small dynamical tendency for self-duality of vacuum in the continuum limit.

Computing the effective Hamiltonian of low-energy vacuum gauge fields

A standard approach to investigate the nonperturbative QCD dynamics is through vacuum models which emphasize the role played by specific gauge field fluctuations, such as instantons, monopoles, or vortexes. The effective Hamiltonian describing the dynamics of the low-energy degrees of freedom in such approaches is usually postulated phenomenologically, or obtained through uncontrolled approximations. In a recent paper, we have shown how lattice field theory simulations can be used to rigorously compute the effective Hamiltonian of arbitrary vacuum models by stochastically performing the path integral over all the vacuum field fluctuations which are not explicitly taken into account. In this work, we present the first illustrative application of such an approach to a gauge theory and we use it to compute the instanton size distribution in $SU(2)$ gluon dynamics in a fully model independent and parameter-free way.