Non-ideal Process Research Articles

Analysis of Defect Tolerance in Molecular Crossbar Electronics

Molecular electronics such as silicon nanowires (NW) and carbon nanotubes (CNT) demonstrate great potential for continuing the technology advances toward future nano-computing paradigm. However, excessive defects from bottom-up stochastic assembly have emerged as a fundamental obstacle for achieving reliable computation using molecular electronics. In this paper, we present an information-theoretic approach to investigate the intrinsic relationship between defect tolerance and inherence redundancy in molecular crossbar systems. By modeling defect-prone molecular crossbars as a non-ideal information processing medium, we determine the information transfer capacity, which can be interpreted as the bound on reliability that a molecular crossbar system can achieve. The proposed method allows us to evaluate the effectiveness of redundancy-based defect tolerance in a quantitative manner. Employing this method, we derive the gap of reliability between redundancy-based defect tolerance and ideal defect-free molecular systems. We also show the implications to the related design optimization problem.

THE NONISOTHERMAL STAGE OF MAGNETIC STAR FORMATION. I. FORMULATION OF THE PROBLEM AND METHOD OF SOLUTION

We formulate the problem of the formation and subsequent evolution of fragments (or cores) in magnetically supported, self-gravitating molecular clouds in two spatial dimensions. The six-fluid (neutrals, electrons, molecular and atomic ions, positively charged, negatively charged, and neutral grains) physical system is governed by the radiation, nonideal magnetohydrodynamic equations. The magnetic flux is not assumed to be frozen in any of the charged species. Its evolution is determined by a newly derived generalized Ohm's law, which accounts for the contributions of both elastic and inelastic collisions to ambipolar diffusion and Ohmic dissipation. The species abundances are calculated using an extensive chemical-equilibrium network. Both MRN and uniform grain size distributions are considered. The thermal evolution of the protostellar core and its effect on the dynamics are followed by employing the gray flux-limited diffusion approximation. Realistic temperature-dependent grain opacities are used that account for a variety of grain compositions. We have augmented the publicly available Zeus-MP code to take into consideration all these effects and have modified several of its algorithms to improve convergence, accuracy, and efficiency. Results of magnetic star formation simulations that accurately track the evolution of a protostellar fragment from a density ≃103 cm−3 to a density ≃1015 cm−3, while rigorously accounting for both nonideal MHD processes and radiative transfer, are presented in a separate paper.

Design Considerations in Hybrid Neural Optimization of Fed-Batch Fermentation for PHB Production by Ralstonia eutropha

Mechanistic models are often inadequate for non-ideal fermentation processes. This has been a major limitation in the commercial success of fed-batch fermentations for poly-β-hydroxybutyrate (PHB), a biopolymer that is potentially better than many synthetic polymers. A previous study with Ralstonia eutropha has shown that optimization through neural networks in place of mechanistic models can help to enhance PHB production substantially. Hybrid models combine the strengths of mechanistic and neural models and minimize their weaknesses. However, there is no unique hybrid neural model for a given application. Therefore, three fundamental hybrid designs have been compared with the neural and mechanistic optimizations done earlier for a fed-batch bioreactor for PHB production. Non-ideal features were introduced by adding Gaussian noise in the two feed streams—glucose and NH4Cl—and incorporating the optimum finite dispersion determined previously. All three hybrid designs were superior to the neural and mechanistic approaches. The best hybrid system, using a weighted combination of mechanistic and neural kinetic rates, generated 140% more of biomass and 330% more of PHB than conventional mechanistic optimization. This was achieved with reduced consumption of the two primary substrates. The supremacy of this hybrid system underlines the complexity of the PHB synthesis network and the merit in combining mechanistic and neural kinetics, and the performance enhancement achieved indicates the feasibility of such a system for an economically viable large-scale PHB fermentation.

Optical Proximity Correction With Linear Regression

An important step in today's integrated circuit (IC) manufacturing is optical proximity correction (OPC). In model-based OPC, masks are systematically modified to compensate for the nonideal optical and process effects of an optical lithography system. The polygons in the layout are fragmented, and simulations are performed to determine the image intensity pattern on the wafer. If the simulated pattern on the wafer does not match the desired one, the mask is perturbed by moving the fragments. This iterative process continues until the pattern on the wafer matches the desired one. Although OPC increases the fidelity of pattern transfer to the wafer, it is quite CPU intensive due to the simulations performed at each iteration. In this paper, linear regression techniques from statistical learning are used to predict the fragment movements. The goal is to reduce the number of iterations required in model-based OPC by using a fast, computationally efficient linear regression solution as the initial guess to model-based OPC. Experimental results show that fragment movement predictions via linear regression model significantly decrease the number of iterations required in model-based OPC, thereby decreasing the product development time in IC design and manufacturing.

On the linear stability of weakly ionized, magnetized planar shear flows

We investigate the effects of ambipolar diffusion and the Hall effect on the stability of weakly-ionized, magnetized planar shear flows. Employing a local approach similar to the shearing-sheet approximation, we solve for the evolution of linear perturbations in both streamwise-symmetric and non-streamwise-symmetric geometries using WKB techniques and/or numerical methods. We find that instability arises from the combination of shear and non-ideal magnetohydrodynamic processes, and is a result of the ability of these processes to influence the free energy path between the perturbations and the shear. They turn what would be simple linear-in-time growth due to current and vortex stretching from shear into exponentially-growing instabilities. Our results aid in understanding previous work on the behaviour of weakly-ionized accretion discs. In particular, the recent finding that the Hall effect and ambipolar diffusion destabilize both positive and negative angular velocity gradients acquires a natural explanation in the more general context of this paper. We construct a simple toy model for these instabilities based upon transformation operators (shears, rotations, and projections) that captures both their qualitative and, in certain cases, exact quantitative behaviour.

Influence of Ethanol on Lipid Membranes: From Lateral Pressure Profiles to Dynamics and Partitioning

We have combined experiments with atomic-scale molecular dynamics simulations to consider the influence of ethanol on a variety of lipid membrane properties. We first employed isothermal titration calorimetry together with the solvent-null method to study the partitioning of ethanol molecules into saturated and unsaturated membrane systems. The results show that ethanol partitioning is considerably more favorable in unsaturated bilayers, which are characterized by their more disordered nature compared to their saturated counterparts. Simulation studies at varying ethanol concentrations propose that the partitioning of ethanol depends on its concentration, implying that the partitioning is a nonideal process. To gain further insight into the permeation of alcohols and their influence on lipid dynamics, we also employed molecular dynamics simulations to quantify kinetic events associated with the permeation of alcohols across a membrane, and to characterize the rotational and lateral diffusion of lipids and alcohols in these systems. The simulation results are in agreement with available experimental data and further show that alcohols have a small but non-vanishing effect on the dynamics of lipids in a membrane. The influence of ethanol on the lateral pressure profile of a lipid bilayer is found to be prominent: ethanol reduces the tension at the membrane-water interface and reduces the peaks in the lateral pressure profile close to the membrane-water interface. The changes in the lateral pressure profile are several hundred atmospheres. This supports the hypothesis that anesthetics may act by changing the lateral pressure profile exerted on proteins embedded in membranes.

Heat of explosion of commercial and brisant high explosives

Methods for determining the heat of explosion of high explosives (HEs) with ideal and nonideal processes of explosive decomposition are considered. It is shown that the heat of explosion is of significance for estimating the efficiency of commercial HEs and is used in the energetic characterization of the working capacity. The heat of explosion of brisant HEs is only part of the blast heat of explosion and is the heat content of gaseous detonation products during their isentropic expansion from the initial state to a certain expansion ratio (determined by experimental conditions). The heat of explosion can be obtained by thermodynamic calculations based on physically justified equations of state for fluids (gaseous detonation products in the chemical-reaction zone of the detonation wave in the supercritical state) and condensed nanocarbon phases (nanographite, nanodiamond, and liquid carbon). Experimental and calculated values of the heat of explosion are given. The thermodynamic calculation is inapplicable to commercial HEs because of the nonideal nature of their detonation. The heat of explosion of commercial HEs can be calculated using the Hess law. The heat of explosion of brisant HEs is not a measure of power. The power of HEs is characterized by the propellant performance. It is shown that even detonation velocity cannot be a measure of the power of HEs. The power and detonation parameters of brisant HEs are determined by the energy release density in unit volume of the chemical-reaction zone of the detonation wave and by the rate of energy release from the shock front rather than by the heat of explosion, which cannot be considered a universal characteristic.

Effect of constitutive laws on plane strain ideal flow design: an analytical example

The major objective of this paper is to clarify the effect of constitutive laws on bulk forming design based on the ideal flow theory. The latter theory is in general applicable for perfectly/plastic materials. However, its kinematics equations constitute a closed-form system, which are valid for any incompressible materials, therefore enabling us to extend design solutions based on the perfectly/plastic constitutive law to more realistic laws with rate sensitive hardening behavior. In the present paper, several constitutive laws commonly accepted for the modeling of cold and hot metal forming processes are considered and the effect of these laws on one particular plane strain design is demonstrated. The closed form solution obtained describes a nontrivial nonsteady ideal process. The design solutions based on the ideal flow theory are not unique. To achieve the uniqueness, the criterion that the plastic work required to deform the initial shape of a given class of shapes into a prescribed final shape attains its minimum is adopted. Comparison with a non-ideal process is also made.

Identification of channelling and recirculation parameters of agitated pulp stock chests

This paper describes a mechanism for identifying the dynamics of non-ideal mixing processes. The object is to study two of the non-ideal behaviours of agitated pulp stock chests: recirculation and channelling. An initial continuous-time model, which contains physically relevant parameters, is transformed into its discrete-time counterpart. This transformation introduces some challenging identification problems, as the discrete-time parameters become a non-linear combination of the original continuous-time parameters. A system identification methodology that addresses these challenges is developed and demonstrated by means of computer simulation. The analysis of data collected from experiments on a laboratory scale model of an industrial chest shows the potential of the techniques developed in this paper.

Herbicide Runoff along Highways. 2. Sorption Control

Controversy remains about the importance of nonlinear sorption isotherms, desorption rate limitations, and aging effects, collectively referred to as nonideal sorption processes, in controlling the fate and transport of organic contaminants. Herbicide runoff from highway soils represents a good test case for assessing the relative importance of nonideal sorption because runoff flow rates are often high, soil-water contacttimes are short, and significant time is available for contaminant aging after application. This study examines the sorption and desorption of five herbicides with a wide range of properties (isoxaben, oryzalin, diuron, clopyralid, and glyphosate) on soil samples from two roadsides in northern California and uses the results to examine field runoff data from multiple rainy seasons. Nonideal sorption processes do not appear to be significant in determining herbicide runoff at the field sites because (i) sorption isotherms were linear or slightly nonlinear for all compounds but glyphosate, (ii) field runoff concentration ratios between isoxaben and oryzalin were consistent with linear partitioning predictions, (iii) runoff leaving the site appeared to be in equilibrium with local soil concentrations, and (iv) desorption distribution coefficients for aged herbicides on soil samples collected from the field site did not differ substantially from those obtained in short-term laboratory adsorption experiments. Collectively, these findings indicate that linear equilibrium models are adequate for predicting the concentration of herbicides in runoff in these field settings and that more complicated nonideal models do not need to be invoked. Vegetated slopes effectively reduced the herbicide loads, with average removals of 35-80% occurring as runoff traversed a 3-m segment 1 m from the edge of the spray zone.

Quantum Zeno effect in non-ideal measurement processes(Quantum Field Theories: Fundamental Problems and Applications)

Quantum Zeno effect in non-ideal measurement processes(Quantum Field Theories: Fundamental Problems and Applications)

Solar flare theory and light curves

During the last few years several models have been developed to explain the onset and energy release in large, eruptive solar flares. Although there is no consensus yet about the precise mechanism which triggers the onset of an eruption, there is a consensus that the mechanism involves the release of magnetic energy stored in the solar corona. Several of the proposed models use an ideal-MHD loss of equilibrium to trigger the eruption, but these models still require magnetic reconnection to extract the bulk of the magnetic energy. Coupling the ideal loss-of-equilibrium process with the non-ideal reconnection processes, and incorporating thermal conduction, chromospheric evaporation, and radiative cooling, shows great promise as a way to account for the light curves of both solar and stellar flares.

The Energy of Detonation: A Fresh Look at Pressure in the Blasthole

Commercial explosives range from pure emulsions to pure ANFO, with blends of these providing interesting alternatives: energy is often adjusted through addition of aluminium, or the control of density. The energy rating of explosives is derived chiefly from detonation codes, which are used to derive expressions for the internal energy change of the detonation products as they do work under expansion. While all codes used for this purpose work on the basis of Ideal detonation, it is common knowledge that commercial explosives operate in the Non-Ideal domain, which affects the mode of energy delivery to the environment. However, since Ideality represents the foundation from which actual performance evolves, it is valuable to examine the intrinsic energy release of a formulation before attempting to understand the influence of Non-Ideality. In examining the Ideal pressure profile of fundamental formulations, remarkable correlation has been found with field performance, and this increases understanding of the influence of various formulation modifications, especially in regard to the stage at which energy is released, and the effect on rockbreaking. This work has emphasised the value of attempting to understand and define better the Non-Ideal detonation process.

3-D photonic circuit technology

Vertically coupled, wafer-bonded III-V semiconductor waveguide devices provide a means to obtain more powerful, compact photonic integrated circuits and allow for the combination of different materials onto a single chip. Various switching, filtering, multiplexing, and beam splitting devices in the InP-InGaAsP and GaAs-AlGaAs systems for signals in the 1550-nm range have been realized. An investigation of optimal optical add-drop multiplexer waveguide layout shapes has been performed through integration of the coupled-mode Riccati equation, providing potential sidelobe levels of less than -32 dB and filter bandwidths over 20% narrower than those of previous devices. Effects of nonideal processing conditions on filter performance are analyzed as well.

The onset of magnetic reconnection in the magnetotail

This paper addresses the onset of collisionless magnetic reconnection in the tail of the Earth’s magnetosphere. The two-and-a-half-dimensional version of a fully electromagnetic particle-in-cell code is used to describe the pre- and post-onset dynamics of reconnection in thin current sheets in the magnetotail. The ion/electron mass ratio is set to 100. The simulation starts out from an apparently stable equilibrium configuration. Applying an external electric field, meant to be caused by magnetic flux transfer to the tail, leads to the formation of a thin current sheet in the center of the plasma sheet. This confirms earlier results obtains with fluid and hybrid-methods. In the thin sheet quasi-static force-balance leads to a substantial decrease of the north-south component of the magnetic field in the center of the sheet. This in turn causes the electrons to become significantly nongyrotropic, such that a tearing mode starts growing. Regarding the nonideal process that supports the electric field in the diffusion region, the simulation results are shown to be consistent with the notion that electron pressure anisotropies associated with the nongyrotropy generate the required diffusive electric fields. The destabilizing role of electron nongyrotropy is confirmed by a simplified analysis of the energy principle for two-dimensional collisionless plasmas.

Effects of decreasing ionospheric pressure and the plasma mixing recess on the solar wind interaction with non-magnetized planets

Abstract The solar wind interaction with the ionosphere of non-magnetized planets is numerically simulated in the framework of 3-D magnetohydrodynamics (MHD) with two-component plasma. In cases 1 and 2, solar extreme ultraviolet (EUV) flux values is set so the peak ionospheric plasma pressure is below and above the incident solar wind dynamic pressure. While the formation of the bow shock and the magnetic barrier in the upstream region is seen in both cases, a clear formation of the ionopause is seen only in case 2. In case 1, the interplanetary magnetic field (IMF) penetrates from the magnetosheath to the dayside ionosphere so as to adjust the ionospheric total pressure. Penetrating IMF affects the vertical motion of the ionospheric plasma. However, formation process of the ionotail is little affected by the penetrating IMF. In bith cases 1 and 2, partial penetration of the IMF occurs from the magnetic barrier to the terminator ionosphere. This nonideal MHD process characterized by the penetration of flowing magnetized plasma into non-magnetized plasma plays a principal role in the mixing interaction between the solar wind and the planetary ionosphere.

Extractable free monomers from self‐cured dental sealants resulting from dispensing errors

High performance liquid chromatography (HPLC) experiments were performed on a series of commercially available self-curing dental sealant materials that were deliberately mismixed. The goal of the experiments was to measure the amount of extractable sealant under conditions of nonideal processing as might happen clinically. The stoichiometry of the two component resins ranged from a 2/1 to a 1/2 catalyst to base mixture using a commercially available self-cure sealant that was to be mixed 1/1 based on the manufacturer's recommendations. Following fabrication the samples were immersed in an ethanol/water mixture as an extraction fluid that was then analyzed using HPLC. Values other than the 1–1 stoichiometry led to a statistically larger extractable content of bis-glycidyl methacrylate relative to the control. The extractable fraction of triethylene glycol dimethacrylate also increased with mismixing, although statistical differences varied somewhat more. Given the increased concerns about the effects of extractable monomers on the endocrine system, there may be an increased need to maintain proper stoichiometry in a clinical setting. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 5–8, 1999

Extractable free monomers from self-cured dental sealants resulting from dispensing errors.

High performance liquid chromatography (HPLC) experiments were performed on a series of commercially available self-curing dental sealant materials that were deliberately mismixed. The goal of the experiments was to measure the amount of extractable sealant under conditions of nonideal processing as might happen clinically. The stoichiometry of the two component resins ranged from a 2/1 to a 1/2 catalyst to base mixture using a commercially available self-cure sealant that was to be mixed 1/1 based on the manufacturer's recommendations. Following fabrication the samples were immersed in an ethanol/water mixture as an extraction fluid that was then analyzed using HPLC. Values other than the 1-1 stoichiometry led to a statistically larger extractable content of bis-glycidyl methacrylate relative to the control. The extractable fraction of triethylene glycol dimethacrylate also increased with mismixing, although statistical differences varied somewhat more. Given the increased concerns about the effects of extractable monomers on the endocrine system, there may be an increased need to maintain proper stoichiometry in a clinical setting.

Effects of decreasing ionospheric pressure on the solar wind interaction with non-magnetized planets

The large-scale solar wind interaction with the ionosphere of non-magnetized planets is numerically simulated in the framework of three-dimensional (3-D) magnetohydrodynamics (MHD) with a two-component plasma. The finite-volume total variation diminishing (TVD) scheme is used to solve this problem. Numerical results are given for two cases of different solar extreme ultraviolet (EUV) flux values. In case 1, solar EUV ionization is set so the peak ionospheric plasma pressure is below the incident solar wind dynamic pressure. In case 2, on the other hand, it is set so the peak ionospheric pressure exceeds the solar wind dynamic pressure. While the formation of the bow shock and the magnetic barrier in the upstream region is seen in both cases, a clear formation of the ionopause is seen only in case 2. In case 1, the interplanetary magnetic field (IMF) penetrates from the magnetosheath to the dayside ionosphere so as to adjust the ionospheric total pressure. Penetrating IMF affects the vertical motion of the ionospheric plasma to cause anomalous stratifications of the terminator ionosphere. However, formation process of the ionotail is little affected by the penetrating IMF. Another important process predicted from the present study is partial penetration of the IMF from the magnetic barrier to the terminator ionosphere. This nonideal MHD process characterized by the penetration of flowing magnetized plasma into non-magnetized plasma plays a principal role in the mixing interaction between the solar wind and the planetary ionosphere.

Capability of convection–dispersion transport models to predict transient water and solute movement in undisturbed soil columns

The capability of the convection–dispersion model coupled with the Richards equation to predict transient transport of water and solutes in porous media is studied in a laboratory soil column. The solutes used are 3H 2O as a conservative tracer and 14C-labeled dibutylphthalate (DBP) as a sorbing solute. To account for multiple nonideal transport processes, a model was developed that may consider hysteresis of the water retention curve, sorption nonequilibrium (sorption kinetics and sorption hysteresis) and mobile and immobile water domains during solute transport. The model parameters were determined independently from the transient experiments, but on the same soil column to avoid uncertainty in transferring results from one sample to another. The hydraulic properties of the soil column were estimated by a multistep outflow experiment using inverse modeling. Transport parameters were estimated form breakthrough curves of 3H 2O measured under steady-state flow conditions. The sorption parameters of DBP were determined using batch techniques. Matrix potentials in the soil could not be predicted using a simple hysteresis model. Whereas the prediction of the tracer transport was satisfactory, it was not successful for DBP, inspite taking all nonequilibrium processes into account. DBP showed an early breakthrough and fluctuations in the outflow concentrations, which were induced by changes in the hydraulic boundary conditions. These fluctuations are caused by exchange processes during redistribution. The results suggest that models based on equilibrium assumptions may not always be suitable to predict the observed transport patterns. A calibration of the multinonequilibrium convective–dispersive model with the measured data, however, was possible.