Concurrent multiresolution finite element: formulation and algorithmic aspects

A multiresolution concurrent theory for heterogenous materials is proposed with novel macro scale and micro scale constitutive laws that include the plastic yield function at different length scales. In contrast to the conventional plasticity, the plastic flow at the micro zone depends on the plastic strain gradient. The consistency condition at the macro and micro zones can result in a set of algebraic equations. Using appropriate boundary conditions, the finite element discretization was derived from a variational principle with the extra degrees of freedom for the micro zones. In collaboration with LSTC Inc, the degrees of freedom at the micro zone and their related history variables have been augmented in LS-DYNA. The 3D multiresolution theory has been implemented. Shear band propagation and the large scale simulation of a shear driven ductile fracture process were carried out. Our results show that the proposed multiresolution theory in combination with the parallel implementation into LS-DYNA can capture the effects of the microstructure on shear band propagation and allows for realistic modeling of ductile fracture process.     

Formulation of implicit finite element methods for multiplicative finite deformation plasticity

Some constitutive and computational aspects of finite deformation plasticity are discussed. Attention is restricted to multiplicative theories of plasticity, in which the deformation gradients are assumed to be decomposable into elastic and plastic terms. It is shown by way of consistent linearization of momentum balance that geometric terms arise which are associated with the motion of the intermediate configuration and which in general render the tangent operator non-symmetric even for associated plastic flow. Both explicit (i.e. no equilibrium iteration) and implicit finite element formulations are considered. An assumed strain formulation is used to accommodate the near-incompressibility associated with fully developed isochoric plastic flow. As an example of explicit integration, the rate tangent modulus method is reviewed in some detail. An implicit scheme is derived for which the consistent tangents, resulting in quadratic convergence of the equilibrium iterations, can be written out in closed form for arbitrary material models. All the geometrical terms associated with the motion of the intermediate configuration and the treatment of incompressibility are given explicitly. Examples of application to void growth and coalescence and to crack tip blunting are developed which illustrate the performance of the implicit method.     

Formulation of garlic oil‐in‐water nanoemulsion: antimicrobial and physicochemical aspects

Despite the unique properties, application of garlic essential oil (GEO) is too limited in food and drugs, due to its low water solubility, very high volatility and unpleasant odour. In this work, a nanoemulsion containing GEO was formulated to cover and protect the volatile compounds of GEO. The encapsulation efficiency of formulated nanoemulsions was measured by gas chromatography and obtained encapsulation efficiency ranged from 91 to 77% for nanoemulsions containing 5–25% GEO, respectively. The 2,2‐diphenyl‐1‐picrylhydrazyl method for antioxidant activity measurement showed that free radical scavenging capacity of nanoemulsions intensified during storage time. The electrical conductivity of the samples was constant over storage time while linearly increased by raising the temperature. Thermogravimetric analysis was used to determine the thermal resistance of nanoemulsions and their ingredients. Interestingly, microbial tests cleared that the control nanoemulsion with a particle size below 100 nm (nanoemulsion without GEO) also showed antimicrobial activity. Disk diffusion method showed that pure GEO and also formulated nanoemulsions had a stronger effect against Gram‐positive bacterium (Staphylococcus aureus) than Gram‐negative bacterium (Escherichia coli).Inspec keywords: emulsions, nanostructured materials, antibacterial activity, microorganisms, electrical conductivity, thermal analysis, thermal resistance, oils, nanobiotechnology, food safety, cellular biophysicsOther keywords: garlic oil‐in‐water nanoemulsion, antimicrobial aspects, physicochemical aspects, garlic essential oil, GEO, volatile compounds, encapsulation efficiency, gas chromatography, 2,2‐diphenyl‐1‐picrylhydrazyl method, antioxidant activity measurement, free radical scavenging capacity, storage time, electrical conductivity, thermogravimetric analysis, thermal resistance, antimicrobial activity, disk diffusion method, Gram‐positive bacterium, Staphylococcus aureus, Gram‐negative bacterium, Escherichia coli     

Computational aspects of incrementally objective algorithms for large deformation plasticity

A methodology for computationally efficient formulation of the tangent stiffness matrix consistent with incrementally objective algorithms for integrating finite deformation kinematics and with closest point projection algorithms for integrating material response is developed in the context of finite deformation plasticity. Numerical experiments illustrate an excellent performance of the proposed formulation in comparison with other algorithms. Copyright © 1999 John Wiley & Sons, Ltd.     

On finite strain poroplasticity with reversible and irreversible porosity laws. Formulation and computational aspects

The main purpose of this paper is the formulation of a poroplastic framework suitable for finite strain and high pore pressure in saturated porous media. Here we make a distinction between poroplasticity with totally reversible porosity and poroplasticity with the occurrence of irreversible porosity. For this latter, an important key point is that the total porosity is not additively decomposed as usual into reversible and irreversible parts. As shown, the permanent porosity is embedded into the definition of the total porosity itself. The approach is built around the physical restriction that the actual Eulerian porosity is bounded in the interval [0, 1] for any admissible process. Elementary considerations motivate the modeling throughout the paper and the formulation is integrated within the unified continuum thermodynamics of open media, which is crucial in setting the convenient forms of the state laws and evolution equations for the flux variables to fully characterize the behavior of porous materials. On the numerical side, the algorithmic design is described in detail for an easy implementation within the context of the finite element method. Finally, we present a set of numerical simulations to illustrate the effectiveness of the proposed framework.     

Two computational primitives for algorithmic self-assembly: copying and counting

Copying and counting are useful primitive operations for computation and construction. We have made DNA crystals that copy and crystals that count as they grow. For counting, 16 oligonucleotides assemble into four DNA Wang tiles that subsequently crystallize on a polymeric nucleating scaffold strand, arranging themselves in a binary counting pattern that could serve as a template for a molecular electronic demultiplexing circuit. Although the yield of counting crystals is low, and per-tile error rates in such crystals is roughly 10%, this work demonstrates the potential of algorithmic self-assembly to create complex nanoscale patterns of technological interest. A subset of the tiles for counting form information-bearing DNA tubes that copy bit strings from layer to layer along their length.     

Extracting alternative machining features: An algorithmic approach

Automated recognition of features from CAD models has been attempted for a wide range of application domains. In this article we address the problem of representing and recognizing a complete class of features in alternative interpretation for a given design.We present a methodology for recognizing a class of machinable features and addressing the computational problems posed by the existence of feature-based alternatives. Our approach addresses a class of volumetric features that describe material removal volumes made by operations on three-axis vertical machining centers, including drilling, pocket-milling, slot-milling, face-milling, chamfering, filleting, and blended surfaces.This approach recognizes intersecting features and is complete over all features in our class; i.e., for any given part, the algorithm produces a set containing all features in our class that correspond to possible operations for machining that part. This property is of particular significance in applications where consideration of different manufacturing alternatives is crucial.This approach employs a class of machinable features expressible as MRSEVs (a STEP-based library of machining features). An example of this methodology has been implemented using the ACIS solid modeler and the National Institute's of Health C++ class library.     

Input Variable Expansion: An algorithmic design generation technique

Input Variable Expansion (IVE) is a domain-independent, algorithmic methodology for generating new designs. These designs are based on a known design which is cast as an optimization problem, described by its first principle equations. IVE performs design space expansion by replicating the topology of the initial design, assigning independent properties to each region, and distributing a selected input to the newly created regions. Optimization information is employed in the selection of the distributed input.The resulting design is optimized, using symbolic optimization techniques when possible. In more complex and industrially relevant problems where symbolic methods are more difficult, numerical methods are used to optimize the resulting designs. Trends over generations of designs are observed and the limiting designs are induced. These designs incorporate new features, and may exhibit either an improved objective or a feasible design space replacing an infeasible one.IVE is a complementary expansion technique to Dimensional Variable Expansion (DVE), developed by Cagan and Agogino (1991a). Together, IVE and DVE initiate a library of design space expansion techniques which, in some cases, eliminate the need for prepostulated superstructures for finding the optimal solution. IVE is demonstrated in the designs of a catalyst bed, a set of columns under axial load, and a chemical reactor network.     

Beyond generic control systems: configuration of customized and algorithmic systems

The paper discusses the state-of-the-art generic control systems, their applicability and limitations. These limitations will be analyzed: they are generally rooted in requirements for specific data collection, man-machine interface problems, uniqueness of the controlled process, and a variety of host hardware and data collection equipment. The solution to these problems resides in the development and use of generic system producing software programs. These programs take analyst specified parameters and automatically generate the software that will implement these parameters. Examples are drawn from electric steel making systems.     

Process and dosage form controlts: Formulation factors

Abstract

During the last decades, there have been considerable developments in the field of pharmaceutics, pharmaceutical technology and product manufacture.

The trend of the pharmaceutical industry is, like in most of the sophisticated industries, to produce, day after day, a better product, and as final goal, to manufacture continueously a perfect drug dosage form.

A few years ago, the defaults were counted in “percent”. After that, it was in per “thousand”. Now it is often expressed in “per million”, or even for very high series (for example empty hard gelatine capsules) the trend is “per billion”. Such an evaluation can only be achieved with a complete control of the whole manufacturing process.

The requirement for pharmaceutical dosage form are numerous (1): adequate biopharmaceutical profile, ease of manufacture, quality assurance (the dosage form must contain the correct quantity of the correct drug, and liberate it at the correct place, at the correct time, and in the correct quantity, with the correct speed), stability, …

These requirements can only be fulfilled with a perfect knowledge of the drug and the dosage form, from the beginning of the development of the dosage form (formulation) to the end of the manufacturing process (production and final product control).

It is the aim of the present lecture to show how important are the formulation factors and what is their influence on the processing and the dosage form control.     

Gradient projection decoding of LDPC codes and algorithmic variations

The current study proposes decoding algorithms for low density parity check codes (LDPC), which offer competitive performance-complexity trade-offs relative to some of the most efficient existing decoding techniques. Unlike existing low-complexity algorithms, which are essentially reduced complexity variations of the classical belief propagation algorithm, starting point in the developed algorithms is the gradient projections (GP) decoding technique, proposed by Kasparis and Evans (2007). The first part of this paper is concerned with the GP algorithm itself, and specifically with determining bounds on the step-size parameter, over which convergence is guaranteed. Consequently, the GP algorithm is reformulated as a message passing routine on a Tanner graph and this new formulation allows development of new low-complexity decoding routines. Simulation evaluations, performed mainly for geometry-based LDPC constructions, show that the new variations achieve similar performances and complexities per iteration to the state-of-the-art algorithms. However, the developed algorithms offer the implementation advantages that the memory-storage requirement is significantly reduced, and also that the performance and convergence speed can be finely traded-off by tuning the step-size parameter.     

Tablet Formulation : Genichi Taguchi's Approach

In this paper the Taguchi Method for studying a large number of factors and interactions with only a few experiments is shortly presented and applied to the development of a tablet formulation.     

A generalized elastoplastic plate theory and its algorithmic implementation

In continuum mechanics within specific classes of problems, one- or two-dimensional theories are often simpler to apply than the more complete three-dimensional one. This is, for example, the case of thin bodies, such as plates or shells, which may be studied using appropriate two-dimensionai theories. Within this approach, the reduction of the dimension is traded for a loss of information relative to the motion in the transverse direction. For example, in the case of non-linear material behaviour, classical plasticity plate theories are usually not able to model the effects related to the spreading of plasticity through the cross-section. In the present paper we discuss a generalized plasticity plate model, which can be used to reproduce some of the three-dimensional effects in a two-dimensional setting. We present the continuous and the discrete time model, including both isotropic and kinematic hardening mechanisms; moreover, the form of the tangent matrix consistent with the discrete model is addressed. Finally, some examples (cantilever beam, clamped circular plate and clamped square plate under monotonic and cyclic loading) are studied numerically using a three-dimensional classical plasticity theory, a classical plasticity plate theory and the proposed plate theory. The generalized plasticity plate model matches the three-dimensional response with greater accuracy, than the classical plasticity plate model.     

Ocular Preparations: The Formulation Approach

ABSTRACT

The main aim of pharmacotherapeutics is the attainment of an effective drug concentration at the intended site of action for a sufficient period of time to elicit the response. A major problem being faced in ocular therapeutics is the attainment of an optimal concentration at the site of action. Poor bioavailability of drugs from ocular dosage forms is mainly due to the tear production, non-productive absorption, transient residence time, and impermeability of corneal epithelium. This article reviews: the barriers that decrease the bioavailability of an ophthalmic drug; the objectives to be considered in producing optimal formulations; and the approaches being used to improve the corneal penetration of a drug molecule and delay its elimination from the eye. The focus of this review is on the recent developments in topical ocular drug delivery systems, the rationale for their use, their drug release mechanism, and the characteristic advantages and limitations of each system. In addition, the review attempts to give various analytical procedures including the animal models and other models required for bioavailability and pharmacokinetic studies. The latter can aid in the design and predictive evaluation of newer delivery systems.

The dosage forms are divided into the ones which affect the precorneal parameters, and those that provide a controlled and continuous delivery to the pre- and intraocular tissues. The systems discussed include: (a) the commonly used dosage forms such as gels, viscosity imparting agents, ointments, and aqueous suspensions; (b) the newer concept of penetration enhancers, phase transition systems, use of cyclodextrins to increase solubility of various drugs, vesicular systems, and chemical delivery systems such as the prodrugs; (c) the developed and under-development controlled/continuous drug delivery systems including ocular inserts, collagen shields, ocular films, disposable contact lenses, and other new ophthalmic drug delivery systems; and (d) the newer trends directed towards a combination of drug delivery technologies for improving the therapeutic response of a non-efficacious drug. The fruitful resolution of the above-mentioned technological suggestions can result in a superior dosage form for both topical and intraocular ophthalmic application.     

Tablet Formulation : Genichi Taguchi's Approach

Abstract

In this paper the Taguchi Method for studying a large number of factors and interactions with only a few experiments is shortly presented and applied to the development of a tablet formulation.