Crack face contact in X‐FEM using a segment‐to‐segment approach

In this study, we propose a segment‐to‐segment contact formulation (mortar‐based) that uses Lagrange's multipliers to establish the contact between crack faces when modeled with the extended finite element method (X‐FEM) in 2D problems. It is shown that, in general, inaccuracies arise when the contact is formulated following a point‐to‐point approach. This is due to the non‐linear character of the X‐FEM interpolation along the crack faces that leads to crack face interpenetration. However, the segment‐to‐segment approach optimizes the fulfilment of the contact constraints along the whole crack segment, and in practice the contact is modeled precisely. Convergence studies for mesh sequences have been performed, showing the advantages of the proposed methodology. Copyright © 2009 John Wiley & Sons, Ltd.     

CALCULATION OF THE STRESS INTENSITY FACTOR AND ESTIMATION OF ITS ERROR BY A SHAPE SENSITIVITY ANALYSIS

Abstract— The precision with which the stress intensity factor (SIF) can be calculated from a finite element solution depends essentially on the extraction method and on the discretization error. In this paper, the influence of the discretization error in the SIF calculation was studied and a method for estimating the resulting error was developed. The SIF calculation method used is based on a shape design sensitivity analysis; this assures that the resulting error in the extracted SIF depends solely on the global discretization error present in the finite element solution. Moreover, this method allows us to extend the Zienkiewicz-Zhu discretization error estimator to the SIF calculation. The reliability of the proposed method was analysed solving a two-dimensional problem using an h -adaptive process. Also the convergence of the error with the h -adaptive refinement was studied.     

Compliance with the "recommendations SEPAR" on spirometry

The objective of this study was to assess Spanish performance of spirometry and to determine the extent to which practice is in accordance with the 1985 SEPAR recommendations. To that end we formulated a questionnaire with 31 items in two sections, 10 covering basic aspects of compliance with necessary techniques and 21 general questions. The questionnaire was sent to all SEPAR members. One hundred eight responses were received. The results show that the typical spirometric measurement was forced expiration without a bronchodilator test by way of a pneumotacograph, with simultaneous representation of the flow/volume curve. Calibration, when performed, is done daily with a 3 1 syringe and atmospheric data are checked. Spirometric measurements are usually obtained by a registered nurse, who also collects anthropometric data directly from the patient. The patient is usually seated with the nose occluded. At least three and at most eight satisfactory readings are obtained. The criteria for starting and ending the maneuver and the reference values used are those recommended by SEPAR. The equipment is washed weekly with soap and water; calibrations and equipment incidences are not recorded. The level of compliance with 1985 SEPAR norms for forced spirometry is adequate with respect to some technical equipment questions but deficient on basic procedure and quality control.     

欣曼科研大厦 美国亚特兰大

正该项目为佐治亚理工学院的一项重要建筑遗产注入了新的活力,将其改建为建筑学院的灵活附属建筑,包括工作室、实验室、教室和研究室。原建筑由一个50英尺高的大跨度工业顶棚,在垂直轴上重新规划,水平轴上保持开放和灵活性。不间断的地板主要作为工作室空间,但也可以重新配置用于大型组件。大跨度空间融入四方院和公共空间城市网络,最大程度的与学院建立联系。对于学校来说,重要的     

The variable nature of Biot numbers in food drying

Biot numbers (Bi) relate internal and external resistances to mass or heat fluxes and are useful to identify controlling mechanisms. Their variation during drying received little attention despite its importance in model selection. Therefore, variable Bi were analysed in drying of wheat, a low-moisture product, and in the formation of a low-calorie, dehydrated apple-leather (LCAL), a high moisture product. Wheat drying was predicted with a numerical solution from a m.c. of 0.35 kg water/kg dry matter, to find a variable mass transfer Bi that shifted the controlling mechanism from internal-external to internal. From a lower m.c. of 0.205 kg water/kg dry matter, the entire process was internally controlled. Drying of shrinking LCAL was solved with the energy balance. The mass transfer Bi varied from 0.5 to 1600, while the heat transfer Bi, only from 0.25 to 0.5, and a modified version, from 0.25 to 0.     

Fluidisation velocities during processing of whole soybean snack

Soybeans contribute to healthy nutrition because of the high proportion and quality of proteins. Its oil content is considerably lower than in peanuts, restricting energy intake. Precooked samples prepared at increasing drying-toasting times (lower moisture contents) experienced shrinkage and deformation.With the aim of determining design parameters for this process, fluid-dynamic studies of samples extracted at several times during drying-toasting allowed us to determine laminar and turbulent coefficients of the Ergun equation and the minimum fluidisation velocity (V_mf), at ambient temperatures. The turbulent coefficient increased for decreasing moistures and V_mf varied from 2.6 and 1.2 m/s over a 60 min process. As drying-toasting must be conducted at 140 °C, an increase by 20% in V_mf is required. Operating velocities were 50% above V_mf to produce uniform treatment. As the system requires a decreasing fluidisation velocity with time, an automatic control with time-varying target value should be devised to limit energy consumption and prevent solid losses.     

Autonomic Computing through Reuse of Variability Models at Runtime: The Case of Smart Homes

Our research shows that autonomic behavior can be achieved by leveraging variability models at runtime. In this way, the modeling effort made at design time is not only useful for producing the system but also provides a richer semantic base for autonomic behavior during execution. The use of variability models at runtime brings new opportunities for autonomic capabilities by reutilizing the efforts invested at design time. Our proposed approach has two aspects: reuse of design knowledge to achieve AC and reuse of existing model-management technologies at runtime. We developed the Model-Based Reconfiguration Engine (MoRE) to implement model-management operations. Our research demonstrates the approach's feasibility for smart homes, especially for self-healing and -configuring capabilities.     

Value Extrapolation Technique to Solve Retrial Queues: A Comparative Perspective

While the retrial phenomenon plays an important role in communication networks and should not be ignored, retrial systems do not present an exact analytic solution, so approximate techniques are required. To the best of our knowledge, all the existing techniques are based on computing the steady states probabilities. We propose another approach based on the relative state values which appear in the Howard equations. The results of the numerical evaluation carried out show that this solution outperforms previous approaches in terms of both accuracy and computation time.     

Gold versus Silver‐Catalyzed Intermolecular Hydroaminations of Alkenes and Dienes

Comparative studies about the hydroamination of unactivated alkenes and dienes catalyzed by either cationic gold(I) triphenyl phosphite complexes or silver salts were performed using sulfonamides, anilines and carbamates as nucleophiles. Gold‐catalyzed reactions generally, need lower loadings than those carried out with silver salts. Simple alkenes react only with sulfonamides and weak aromatic amines such as p‐nitroaniline, whereas for conjugated dienes carbamates can also be used. Carbon‐carbon double bond isomerization is observed only with gold similarly to when triflic acid was used, affording mixtures of regioisomeric products in the same cases. Silver‐catalyzed hydroaminations failed with terminal alkenes, except with styrenes. Conjugate dienes can be hydroaminated either at 85 °C in toluene or at room temperature in dichloromethane. Non‐conjugated 1,4‐ and 1,5‐dienes suffer double hydroamination leading to saturated N‐tosylated heterocyclic amines The catalytic cycle for the silver(I)‐catalyzed hydroamination process has been computationally analyzed, resembling gold(I)‐catalyzed processes, although with some significant differences.