Shakedown analysis of a torispherical head with a piping nozzle under combined loads by the stress compensation method

Shakedown assessment is an important task in determining the load-bearing capacity of structures and evaluating their safety. The traditional shakedown analyses, which are based on the upper or lower bound shakedown theorem to establish the mathematical programming formulation and solve an optimisation problem, are difficult to apply in engineering practice owing to limitations of the computing scale and computational efficiency. In this study, a numerical shakedown analysis using the recently developed stress compensation method (SCM) is performed for a torispherical head with a piping nozzle, which is a typical structural component of pressure vessel equipment. The loads applied to the structural component include an internal pressure, axial force, twisting moment, out-of-plane and in-plane bending moments, and thermal loading, all of which vary independently of each other. Two- and three-dimensional strict shakedown boundaries for the torispherical head under different combinations of these loads are presented and analysed. In addition, the effect of a temperature-dependent yield strength on the shakedown domain is also investigated. These investigations demonstrate that the proposed SCM is capable of solving the practical shakedown problem for structures under complicated combined loads in industrial applications. The obtained results can provide guidance for the safe structural design of torispherical heads with piping nozzles

An open-label clinical trial of agalsidase alfa enzyme replacement therapy in children with Fabry disease who are naïve to enzyme replacement therapy.

BackgroundFollowing a drug manufacturing process change, safety/efficacy of agalsidase alfa were evaluated in enzyme replacement therapy (ERT)-naïve children with Fabry disease.MethodsIn an open-label, multicenter, Phase II study (HGT-REP-084; Shire), 14 children aged ≥7 years received 0.2 mg/kg agalsidase alfa every other week for 55 weeks. Primary endpoints: safety, changes in autonomic function (2-hour Holter monitoring). Secondary endpoints: estimated glomerular filtration rate, left ventricular mass index (LVMI), midwall fractional shortening, pharmacodynamic parameters, and patient-reported quality-of-life.ResultsAmong five boys (median 10.2 [range 6.7, 14.4] years) and nine girls (14.8 [10.1, 15.9] years), eight patients experienced infusion-related adverse events (vomiting, n=4; nausea, n=3; dyspnea, n=3; chest discomfort, n=2; chills, n=2; dizziness, n=2; headache, n=2). One of these had several hypersensitivity episodes. However, no patient discontinued for safety reasons and no serious adverse events occurred. One boy developed immunoglobulin G (IgG) and neutralizing antidrug antibodies. Overall, no deterioration in cardiac function was observed in seven patients with low/abnormal SDNN (standard deviation of all filtered RR intervals; <100 ms) and no left ventricular hypertrophy: mean (SD) baseline SDNN, 81.6 (20.9) ms; mean (95% confidence interval [CI]) change from baseline to week 55, 17.4 (2.9, 31.9) ms. Changes in SDNN correlated with changes in LVMI (r=-0.975). No change occurred in secondary efficacy endpoints: mean (95% CI) change from baseline at week 55 in LVMI, 0.16 (-3.3, 3.7) g/m(2.7); midwall fractional shortening, -0.62% (-2.7%, 1.5%); estimated glomerular filtration rate, 0.15 (-11.4, 11.7) mL/min/1.73 m(2); urine protein, -1.8 (-6.0, 2.4) mg/dL; urine microalbumin, 0.6 (-0.5, 1.7) mg/dL; plasma globotriaosylceramide (Gb3), -5.71 (-10.8, -0.6) nmol/mL; urinary Gb3, -1,403.3 (-3,714.0, 907.4) nmol/g creatinine, or clinical quality-of-life outcomes.ConclusionFifty-five weeks' agalsidase alfa ERT at 0.2 mg/kg every other week was well tolerated. Disease progression may be slowed when ERT is started prior to major organ dysfunction.Trial registrationhttps://ClinicalTrials.gov identifier NCT01363492

A new four-dimensional ratcheting boundary : derivation and numerical validation

A new four-dimensional ratcheting boundary is derived analytically for the first time considering the interaction among four types of stresses: constant mechanical membrane stress, mechanical bending stress, cyclic thermal membrane stress, and thermal bending stress. A uniaxial beam model is used to derive the closed-form ratcheting boundary for these combined cyclic and constant loadings. The Tresca yield condition and elastic-perfectly plastic behavior are assumed. A novel two-plane FE model is proposed for numerical validation and the results predicted by analytical solution agree very well with that obtained by two-plane FE model. The solution of the classical Bree problem is the one of special cases when this new four-dimensional ratcheting boundary is reduced into two-dimensional style. The relationship between the three-dimensional ratcheting boundary adopted by the newly implemented ASME VIII -2 Pressure Vessel Code and the proposed four-dimensional ratcheting boundary is also discussed

A Chemical Screen for Biological Small Molecule-RNA Conjugates Reveals CoA-Linked RNA

Compared with the rapidly expanding set of known biological roles for RNA, the known chemical diversity of cellular RNA has remained limited primarily to canonical RNA, 3'-aminoacylated tRNAs, nucleobase-modified RNAs, and 5'-capped mRNAs in eukaryotes. We developed two methods to detect in a broad manner chemically labile cellular small molecule-RNA conjugates. The methods were validated by the detection of known tRNA and rRNA modifications. The first method analyzes small molecules cleaved from RNA by base or nucleophile treatment. Application to Escherichia coli and Streptomyces venezuelae RNA revealed an RNA-linked hydroxyfuranone or succinyl ester group, in addition to a number of other putative small molecule-RNA conjugates not previously reported. The second method analyzes nuclease-generated mononucleotides before and after treatment with base or nucleophile and also revealed a number of new putative small molecule-RNA conjugates, including 3'-dephospho-CoA and its succinyl-, acetyl-, and methylmalonyl-thioester derivatives. Subsequent experiments established that these CoA species are attached to E. coli and S. venezuelae RNA at the 5' terminus. CoA-linked RNA cannot be generated through aberrant transcriptional initiation by E. coli RNA polymerase in vitro, and CoA-linked RNA in E. coli is only found among smaller (approximately < 200 nucleotide) RNAs that have yet to be identified. These results provide examples of small molecule-RNA conjugates and suggest that the chemical diversity of cellular RNA may be greater than previously understood.Chemistry and Chemical Biolog

Shakedown analysis of modified Bree problems involving thermal membrane stress and generalized loading conditions

For industrial components such as pressure vessels and piping systems, it is important to determine the shake- down domains of structures under complex variable thermo-mechanical loads to avoid low cycle fatigue due to alternating plasticity or incremental plastic collapse caused by ratcheting. In this paper, the interaction among three common types of stresses are considered based on a plane model, namely, mechanical membrane stress, thermal membrane stress and thermal bending stress. Strict shakedown analysis is performed based on the Linear Matching Method under multiple variable mechanical and thermal loads. Three-dimensional shakedown do- mains for three types of modified Bree problems involving thermal membrane stress and generalized loading conditions are given for the first time, and the three-dimensional shakedown boundaries are expressed as two- dimensional parametric equations by introducing a new parameter called "secondary membrane bending ratio" R. By comparing the 3S criterion plane with the newly obtained 3D shakedown boundaries, the conservatism and non-conservatism of the 3S criterion are discussed under different loading paths. As an extension of the 3S criterion, a new and economical criterion on elastic shakedown assessment is proposed for generalized thermo-mechanical loading. The proposed shakedown boundary parametric equations and shakedown checking method can provide guidance for engineering design and safety assessment

Robots Looking for Interesting Things: Extremum Seeking Control on Saliency Maps

Abstract-This paper presents a novel approach to increase the amount of visual stimuli in sensor measurements using saliency maps. A saliency map is a combination of normalized feature maps in different channels (i.e. color, intensity) to represent the relative strength of visual stimuli in an image. The total saliency is higher when the camera is looking at a scene with more interesting things in the field of view and vise versa. We employ methods of extremum seeking control to find a camera position that corresponds to local maximum saliency value. We combine the global properties of simplex optimization methods with the local search properties and dynamic response of extremum seeking control to create a novel algorithm that is more likely to find a global maximum than conventional extremum seeking control. Simulations and experiments are presented to show the strength of this approach

Shakedown analysis of engineering structures under multiple variable mechanical and thermal loads using the stress compensation method

The determination of shakedown load or shakedown domain is an important task in structural design and integrity assessment. In this paper, a novel numerical procedure based on the Stress Compensation Method (SCM) is developed to perform shakedown analysis of engineering structures under multiple variable mechanical and thermal loads. By applying the compensation stress on the yield regions that occur at every load vertex of the prescribed loading domain to adjust the total stress to the yield surface and re-solving the equilibrium equations, the statically admissible residual stress field for static shakedown analysis is constructed. A robust and effective iteration control technique with some convergence parameters is used to check the change of the compensation stress in the inner loop and to update the shakedown load multiplier in the outer loop. For the purpose of general use, the method is implemented into ABAQUS platform. The shakedown problems for the Bree plate, a square plate with a central circular hole and a practical thick vessel with nozzles under some two-dimensional and three-dimensional loading domains are effectively solved and analyzed. Both alternating plasticity mechanism and ratcheting mechanism to determine the shakedown boundary of these structures are revealed. Numerical applications show that the proposed method has good numerical stability, high accuracy and efficiency, and is well suited for shakedown analysis of large-scale practical engineering structures