Experimental results regarding the influence of initial ovality on local buckling under external pressure (collapse) of oil industry tubulars

An important load which can considerably affect the resistance capacity of oil industry tubulars (mainly casing and tubing in high pressure wells, and submarine pipelines installed in deep waters) is the external pressure, causing the pipe collapse phenomenon. Some of the factors with the greatest influence on pipe collapse behaviour are its geometrical imperfections (ovality, eccentricity, etc.). This paper presents the results of research activities aimed to investigate the influence of the pipe initial ovality on the external pressure collapse phenomenon, in order to define design methodologies and criteria for assessing the external pressure resistance capacity of oil industry tubulars. To that purpose, some tests have been performed on small scale pipe specimens, based on the similitude law, and their results have been compared with the calculation formulas usually used to assess pipe collapse resistance capacity considering the influence of initial ovality. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1090

Analysis of the residual stress level in casing and its influence on the collapse strength

The collapse resistance of casing is influenced by many factors, among which the level of residual stresses is an essential one. This paper presents the results of research activities aimed to determine such stress level in seamless tube specimens made of grade N80 steel. These activities included: the selection – based on experimental and theoretical studies – of the most adequate method to determine the residual circumferential stresses in tubes for well casing; a series of experimental tests to define the level of such residual stresses and its variation across the tube thickness; finally, an evaluation of the influence of such stresses upon the value of the collapse pressure of casing. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1156

Diastereomeric dinickel(ii) complexes with non-innocent bis(octaazamacrocyclic) ligands: isomerization, spectroelectrochemistry, DFT calculations and use in catalytic oxidation of cyclohexane

Diastereomeric dinickel(ii) complexes with bis-octaazamacrocyclic 15-membered ligands [Ni(L1-3-L1-3)Ni] (4-6) have been prepared by oxidative dehydrogenation of nickel(ii) complexes NiL1-3 (1-3) derived from 1,2- and 1,3-diketones and S-methylisothiocarbohydrazide. The compounds were characterized by elemental analysis, ESI mass spectrometry, and IR, UV-vis, 1H NMR, and 13C NMR spectroscopy. Single crystal X-ray diffraction (SC-XRD) confirmed the isolation of the anti and syn isomers of bis-octaazamacrocyclic dinickel(ii) complexes 4a and 4s, the syn-configuration of 5s and the anti-configuration of the dinickel(ii) complex 6a. Dimerization of prochiral nickel(ii) complexes 1-3 generates two chiral centers at the bridging carbon atoms. The anti-complexes were isolated as meso-isomers (4a and 6a) and the syn-compounds as racemic mixtures of R,R/S,S-enantiomers (4s and 5s). The syn-anti isomerization (epimerization) of the isolated complexes in chloroform was disclosed. The isomerization kinetics of 5a was monitored at five different temperatures ranging from 20 °C to 50 °C by 1H NMR spectroscopy indicating the clean conversion of 5a into 5s. The activation barrier determined from the temperature dependence of the rate constants via the Eyring equation was found to be ΔH‡ = 114 ± 1 kJ mol−1 with activation entropy ΔS‡ = 13 ± 3 J K−1 mol−1. The complexes contain two low-spin nickel(ii) ions in a square-planar coordination environment. The electrochemical behavior of 4a, 4s, 5s and 6a and the electronic structure of the oxidized species were studied by UV-vis-NIR-spectroelectrochemistry (SEC) and DFT calculations indicating the redox non-innocent behavior of the complexes. The dinickel(ii) complexes 4a, 4s, 5s and 6a/6s were investigated as catalysts for microwave-assisted solvent-free oxidation of cyclohexane by tert-butyl hydroperoxide to produce a mixture of cyclohexanone and cyclohexanol (KA oil). The best value for KA oil yield (16%) was obtained with a mixture of 6a/6s after 2 h of microwave irradiation at 100 °C. © 2022 The Royal Society of Chemistry

DGSim : comparing grid resource management architectures through trace-based simulation

Many advances in grid resource management are still required to realize the grid computing vision of the integration of a world-wide computing infrastructure for scientific use. The pressure for advances is increased by the fast evolution of single, large clusters, which are the primary technological alternative to grids. However, advances in grid resource management cannot be achieved without an appropriate toolbox, of which simulation environments form an essential part. The current grid simulation environments still lack important workload and system modeling features, and research productivity features such as automated experiment setup and management. In this paper we address these issues through the design and a reference implementation of DGSim, a framework for simulating grid resource management architectures. DGSim introduces the concepts of grid evolution and of job selection policy, and extends towards realism the current body of knowledge on grid inter-operation, on grid dynamics, and on workload modeling. We also show through two real use cases how DGSim can be used to compare grid resource management architectures

Phenotyping of idiopathic pulmonary arterial hypertension : a registry analysis

Background Among patients meeting diagnostic criteria for idiopathic pulmonary arterial hypertension (IPAH), there is an emerging lung phenotype characterised by a low diffusion capacity for carbon monoxide (DLCO) and a smoking history. The present study aimed at a detailed characterisation of these patients. Methods We analysed data from two European pulmonary hypertension registries, COMPERA (launched in 2007) and ASPIRE (from 2001 onwards), to identify patients diagnosed with IPAH and a lung phenotype defined by a DLCO of less than 45% predicted and a smoking history. We compared patient characteristics, response to therapy, and survival of these patients to patients with classical IPAH (defined by the absence of cardiopulmonary comorbidities and a DLCO of 45% or more predicted) and patients with pulmonary hypertension due to lung disease (group 3 pulmonary hypertension). Findings The analysis included 128 (COMPERA) and 185 (ASPIRE) patients with classical IPAH, 268 (COMPERA) and 139 (ASPIRE) patients with IPAH and a lung phenotype, and 910 (COMPERA) and 375 (ASPIRE) patients with pulmonary hypertension due to lung disease. Most patients with IPAH and a lung phenotype had normal or near normal spirometry, a severe reduction in DLCO, with the majority having no or a mild degree of parenchymal lung involvement on chest computed tomography. Patients with IPAH and a lung phenotype (median age, 72 years [IQR 65–78] in COMPERA and 71 years [65–76] in ASPIRE) and patients with group 3 pulmonary hypertension (median age 71 years [65–77] in COMPERA and 69 years [63–74] in ASPIRE) were older than those with classical IPAH (median age, 45 years [32–60] in COMPERA and 52 years [38–64] in ASPIRE; p<0·0001 for IPAH with a lung phenotype vs classical IPAH in both registries). While 99 (77%) patients in COMPERA and 133 (72%) patients in ASPIRE with classical IPAH were female, there was a lower proportion of female patients in the IPAH and a lung phenotype cohort (95 [35%] COMPERA; 75 [54%] ASPIRE), which was similar to group 3 pulmonary hypertension (336 [37%] COMPERA; 148 [39%] ASPIRE]). Response to pulmonary arterial hypertension therapies at first follow-up was available from COMPERA. Improvements in WHO functional class were observed in 54% of patients with classical IPAH, 26% of patients with IPAH with a lung phenotype, and 22% of patients with group 3 pulmonary hypertension (p<0·0001 for classical IPAH vs IPAH and a lung phenotype, and p=0·194 for IPAH and a lung phenotype vs group 3 pulmonary hypertension); median improvements in 6 min walking distance were 63 m, 25 m, and 23 m for these cohorts respectively (p=0·0015 for classical IPAH vs IPAH and a lung phenotype, and p=0·64 for IPAH and a lung phenotype vs group 3 pulmonary hypertension), and median reductions in N-terminal-pro-brain-natriuretic-peptide were 58%, 27%, and 16% respectively (p=0·0043 for classical IPAH vs IPAH and a lung phenotype, and p=0·14 for IPAH and a lung phenotype vs group 3 pulmonary hypertension). In both registries, survival of patients with IPAH and a lung phenotype (1 year, 89% in COMPERA and 79% in ASPIRE; 5 years, 31% in COMPERA and 21% in ASPIRE) and group 3 pulmonary hypertension (1 year, 78% in COMPERA and 64% in ASPIRE; 5 years, 26% in COMPERA and 18% in ASPIRE) was worse than survival of patients with classical IPAH (1 year, 95% in COMPERA and 98% in ASPIRE; 5 years, 84% in COMPERA and 80% in ASPIRE; p<0·0001 for IPAH with a lung phenotype vs classical IPAH in both registries). Interpretation A cohort of patients meeting diagnostic criteria for IPAH with a distinct, presumably smoking-related form of pulmonary hypertension accompanied by a low DLCO, resemble patients with pulmonary hypertension due to lung disease rather than classical IPAH. These observations have pathogenetic, diagnostic, and therapeutic implications, which require further exploration