Flexural wave propagation behavior of lumped mass approximations

The suitability of lumped masses for elastic wave propagation problems in beams is investigated. Dispersion relations are presented for lumped mass Euler-Bernoulli elements and an element with shear correction; for purposes of comparison, the dispersive properties of consistent masses are also given. It is shown that by increasing the rotational mass through a rotational mass factor , a good approximation can be obtained to the Timoshenko dispersion relation. Comparison with an exact solution for the propagation of a velocity discontinuity shows that the shear correction is required for a good solution and indicates optimal values for .     

Categorization of Lung Morphology Based on FRC and Height: Computer Simulations of Aerosol Deposition

The aim of this study was to compare the human subject experimental measurements of particle deposition within the lungs using the aerosol bolus technique with the results of analytical modeling as a basis for assessing the influence of lung morphology on inhaled particle deposition patterns. A methodology for scaling the lung morphology, based on a classic symmetric dichotomous model, as a function of both functional residual capacity and height of the investigated population is presented. Because of the availability of deposition data for male and female lung morphologies, these were used as an example to address the importance of adjusting lung morphology in calculating the aerosol deposition rates. In order to represent the 2 groups based on gender enrolled in the experimental study, 2 lung morphologies have been built. An analytical and mechanistic model was used to mimic the bolus delivery technique and simulate the aerosol deposition in each of the 2 groups. Predicted results were compared with experimental data for both total deposition fraction and bolus recovery (fraction of exhaled particles compared with inhaled particles) for 3 flow rates and 3 particle sizes. Good agreement was found between theoretical and measured data, showing the primary importance of the differentiation of the lung morphology to predict the aerosol deposition within human lungs. This study presents a morphological lung model that is adaptable to specific populations (e.g., gender or race), groups (e.g., a clinical study population), or even individuals.

Copyright 2012 American Association for Aerosol Research     

Absolute determination of reaction mechanisms by in situ measurements of reaction intermediates

This paper presents a general methodology to determine reaction mechanisms using in situ measurement of concentration and reaction rate of intermediates. The criteria for testing the validity of a reaction sequence are discussed. An example is given for a heterogeneous catalytic reaction, the decomposition of ozone on manganese oxide. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Oxidation of the Aldehyde Groups in Dialdehyde Starch

This paper describes the difference in relative reactivity of the aldehyde groups present in dialdehyde starch towards different oxidising agents. The oxidation of dialdehyde starch with peracetic acid and sodium bromide leads to only partial oxidation to give mono‐aldehyde‐carboxy starch, while oxidation with sodium chlorite results in dicarboxy derivatives. In order to obtain a more in depth insight into this phenomenon, the products obtained after partial oxidation via both routes were isolated and characterised. The results showed a pronounced difference in preferences between the two carbonyl groups towards the different oxidising agents.     

API 579: a comprehensive fitness-for-service guide

This article presents an overview of the recently published American Petroleum Institute (API) Recommended Practice 579, which covers fitness-for-service assessment of pressure equipment in petrochemical and other industries. Although API 579 covers a wide range of flaws and damage mechanisms, including local metal loss, pitting corrosion, blisters, weld misalignment, and fire damage, the emphasis of the present article is on the assessment of crack-like flaws. The API 579 procedure for evaluating cracks incorporates a failure assessment diagram (FAD) methodology very similar to that in other documents, such as the British Energy R6 approach and the BS 7910 method. The API document contains an extensive compendium of K solutions, including a number of new cases generated specifically for API 579. In the initial release of the document, API has adopted existing reference stress solutions for the calculation of L_r in the FAD procedure. In a future release, however, API plans to replace these solutions with values based on a more rational definition of reference stress. These revised reference stress solutions will incorporate the effect of weld mismatch. In addition to the Appendices of K and reference stress solutions, API 579 includes appendices that provide guidance on estimating fracture toughness and weld residual stress distributions. Over the next few years these appendices will be enhanced with advances in technology. Recently, API has entered into discussions with the American Society of Mechanical Engineers (ASME) to convert API 579 into a joint API/ASME fitness-for-service guide.     

Contact-impact by the pinball algorithm with penalty and Lagrangian methods

Contact-impact algorithms, which are sometimes called slideline algorithms, are a computationally time-consuming part of many explicit simulations of non-linear problems because they involve many branches, so they are not amenable to vectorization, which is essential for speed on supercomputers. The pinball algorithm is a simplified slideline algorithm which is readily vectorized. Its major idea is to embed pinballs in surface elements and to enforce the impenetrability condition only to pinballs. It can be implemented in either a Lagrange multiplier or penalty method. It is shown that, in any Lagrange multiplier method, no iterations are needed to define the contact surface. Examples of solutions and running times are given.     

A functional processor for the relational algebra on a microcomputer

We have built on the U.C.S.D. P-system (running on an IBM Personal Computer) a relational algebra processor, MRDS/FS, which is extremely powerful and which supports a functional syntax for the programmer-user. The relational algebra is provided in the extended operators μ-join, σ-join, project and select. The domain algebra is fully implemented for the first time, giving operations on attributes: arithmetic, logic, comparison and four different categories of aggregation of these. A strictly functional syntax is provided, permitting user-defined functions using the relational and domain algebras as primitive operations. An interactive editor permits the creation, copying and changing of both relations and user-defined functions.